MCQ Questions Chapter 3 Current Electricity Class 12 Physics

Please refer to MCQ Questions Chapter 3 Current Electricity Class 12 Physics with answers provided below. These multiple-choice questions have been developed based on the latest NCERT book for class 12 Physics issued for the current academic year. We have provided MCQ Questions for Class 12 Physics for all chapters on our website. Students should learn the objective based questions for Chapter 3 Current Electricity in Class 12 Physics provided below to get more marks in exams.

Chapter 3 Current Electricity MCQ Questions

Please refer to the following Chapter 3 Current Electricity MCQ Questions Class 12 Physics with solutions for all important topics in the chapter.

MCQ Questions Answers for Chapter 3 Current Electricity Class 12 Physics

Question. The daniel cell is balanced on 125 cm length of a potentiometer. Now, the cell is short circuited by a resistance of 2 Ω and the balance point is obtained at 100 cm. The internal resistance of the daniel cell is
(a) (4/3) Ω
(b) 1.5 Ω
(c) 1.25 Ω
(d) 0.5 Ω

Question. A current of 2 A flows through a 2 Ω resistor when connected across a battery. The same battery supplies a current of 0.5 A when connected across a 9 Ω resistor. The internal resistance of the battery is

Question. Which of the following statements is false?
(a) In a balanced Wheatstone bridge, if the cell and the galvanometer are exchanged, the null point is disturbed
(b) A rheostat can be used as a potential divider
(c) Kirchhoff’s second law represents energy conservation
(d) Wheatstone bridge is the most sensitive when all the four resistances are of the same order of magnitude

Question. In a large building, there are 15 bulbs of 40 W, 5 bulbs of 100 W, 5 fans of 80W and 1 heater of 1 kW. The voltage of the electric mains is 220 V. The minimum capacity of the main fuse of the building will be
(a) 8 A
(b) 10 A
(c) 12 A
(d) 14 A

Question. The supply voltage in a room is 120 V. The resistance of the lead wires is 6 Ω. A 60W bulb is already switched on. What is the decrease of voltage across the bulb, when a 240 W heater is switched on in parallel to the bulb?
(a) zero
(b) 2.9 V
(c) 13.3 V
(d) 10.4V

Question. Dimensions of a block are 1 cm × 1 cm × 100 cm. If specific resistance of its material is 3 × 10^–7 Ω m, then the resistance between the opposite rectangular faces is
(a) 3 × 10^–7 Ω
(b) 3 × 10^–9 Ω
(c) 3 × 10^–5 Ω
(d) 3 × 10^–3 Ω

Question. Pick out the wrong statement.
(a) In a simple battery circuit, the point of lowest potential is the negative terminal of the battery.
(b) The resistance of an incandescent lamp is greater when the lamp is switched off.
(c) An ordinary 100 W lamp has less resistance than a 60 W lamp.
(d) At constant voltage, the heat developed in a uniform wire varies inversely as the length of the wire used.

Question. Three resistors 1 Ω, 2 Ω and 3 Ω are connected to form a triangle. Across 3 W resistor a 3 V battery is connected. The current through 3 W resistor is
(a) 0.75 A
(b) 1 A
(c) 2 A
d) 1.5 A

Question. Charge passing through a conductor of cross-section area A = 0.3 m² is given by q = 3t² + 5t + 2 in coulomb, where t is in second. What is the value of drift velocity at t = 2 s?
(Given, n = 2 × 10²⁵ m^–3)
(a) 0.77 × 10^–5 m s^–1
(b) 1.77 × 10^–5 m s^–1
(c) 2.08 × 10^–5 m s^–1
(d) 0.57 × 10^–5 m s^–1

Question. Five resistances are connected as shown in the figure. The effective resistance between points A and B is

Question. A potentiometer is connected across A and B and a balance is obtained at 64.0 cm. When potentiometer lead to B is moved to C, a balance is found at 8.0 cm. If the potentiometer is now connected across B and C, a balance will be found at

(a) 8.0 cm
(b) 56.0 cm
(c) 64.0 cm
(d) 72.0 cm

Question. 2.5 faraday of electricity is passed through a CuSO₄ solution. The number of gram equivalents of copper deposited on the cathode is
(a) 1
(b) 1.5
(c) 2
(d) 2.5

Question. Each resistance shown in figure is 2 Ω. The equivalent resistance between A and B is

(a) 2 Ω
(b) 4 Ω
(c) 8 Ω
(d) 1 Ω

Question. A 2 V battery, a 15 Ω resistor and a potentiometer of 100 cm length, all are connected in series. If the resistance of potentiometer wire is 5 Ω, then the potential gradient of the potentiometer wire is
(a) 0.005 V cm^–1
(b) 0.05 V cm^–1
(c) 0.02 V cm^–1
(b) 0.2 V cm^–1

Question. A cell in secondary circuit gives null deflection for 2.5 m length of potentiometer having 10 m length of wire. If the length of the potentiometer wire is increased by 1 m without changing the cell in the primary, the position of the null point now is
(a) 3.5 m
(b) 3 m
(c) 2.75 m
(d) 2.0 m

Question. Equal amounts of metal are converted into cylindrical wires of different lengths (L) and cross-sectional area (A). The wire with the maximum resistance is the one, which has
(a) length = L and area = A
(b) length = L/2 and area = 2A
(c) length = 2L and area = A/2
(d) all have the same resistance, as the amount of the metal is the same.

Question. The ratio of the amounts of heat developed in the four arms of a balance Wheatstone bridge, when the arms have resistances P = 100 Ω, Q = 10 Ω, R = 300 Ω and S = 30 W respectively is
(a) 3 : 30 : 1 : 10
(b) 30 : 3 : 10 : 1
(c) 30 : 10 : 1 : 3
(d) 30 : 1 : 3 : 10

Question. On interchanging the resistances, the balance point of a meter bridge shifts to the left by 10 cm. The resistance of their series combination is 1kW. How much was the resistance on the left slot before interchanging the resistances?
(a) 990 Ω
(b) 910 Ω
(c) 900 Ω
(d) 550 Ω

Question. In a potentiometer experiment, it is found that no current passes through the galvanometer when the terminals of the cell are connected across 52 cm of the potentiometer wire. If the cell is shunted by a resistance of 5Ω, a balance is found when the cell is connected across 40 cm of the wire. Find the internal resistance of the cell.
(a) 1Ω
(b) 2 Ω
(c) 1 5 .Ω
(d) 2 5 .Ω

Question. When a current of 5 mA is passed through a galvanometer having a coil of resistance 15 Ω, it shows full scale deflection. The value of the resistance to be put in series with the galvanometer to convert it into a voltmeter of range 0-10 V is
(a) 2 045 x 10³ Ω
(b) 2 535 x 10³ Ω
(c) 4 005 x 10³ Ω
(d) 1985 x 10³ Ω

Question. In the adjacent shown circuit, a voltmeter of internal resistance R, when connected across B and C reads (100/3)V. Neglecting the internal resistance of the battery, the value of R is

(a) 100 kΩ
(b) 75 kΩ
(c) 50 kΩ
(d) 25 kΩ

Question. A solid sphere of radius R₁ and volume charge density r = P₀/r is enclosed by a hollow sphere of radius R₂ with negative surface charge density s, such that the total charge in the system is zero. r₀ is a positive constant and r is the distance from the centre of the sphere. The ratio R₂/R₁ is

Question. An electric kettle takes 4 A current at 220 V. How much time will it take to boil 1 kg of water from temperature 20°C? The temperature of boiling water is 100°C.
(a) 12.6 min
(b) 4.2 min
(c) 6.3 min
(d) 8.4 min

Question. 50 Ω and 100 Ω resistors are connected in series. This connection is connected with a battery of 2.4 V. When a voltmeter of 100 Ω resistance is connected across 100 Ω resistor, then the reading of the voltmeter will be
(a) 1.6 V
(b) 1.0 V
(c) 1.2 V
(d) 2.0 V

Question. There are a 25 Ω – 220 V bulb and a 100 Ω – 220 V line. Which electric bulb will glow more brightly?
(a) 25 Ω bulb
(b) 100 Ω bulb
(c) Both will have equal incandescence
(d) Neither 25 Ω nor 100 Ω bulb will give light

Question. In Meter bridge or Wheatstone bridge for measurement of resistance, the known and the unknown resistances are interchanged. The error so removed is
(a) end correction
(b) index error
(c) due to temperature effect
(d) random error

Question. Three resistances of 4 W each are connected as shown in figure. If the point D divides the resistance into two equal halves, the resistance between point A and D will be

(a) 12 Ω
(b) 6 Ω
(c) 3 Ω
(d) 1/3 Ω. 

Question. Identify the incorrect statement regarding a superconducting wire
(a) transport current flows through its surface
(b) transport current flows through the entire area of cross-section of the wire
(c) it exhibits zero electrical resistivity and expels applied magnetic field
(d) it is used to produce large magnetic field.

Question. When an electrical appliance is switched on, it responds almost immediately, because
(a) the electrons in the connecting wires move with the speed of light
(b) the electrical signal is carried by electromagnetic waves moving with the speed of light
(c) the electrons move with speed which is close to but less than speed of light
(d) the electron are stagnant

Question. The resistance of a metal increases with increasing temperature because
(a) the collisions of the conducting electrons with the electrons increase
(b) the collisions of the conducting electrons with the lattice consisting of the ions of the metal increase
(c) the number of conduction electrons decreases
(d) the number of conduction electrons increases.

Question. In the absence of applied potential, the electric current flowing through a metallic wire is zero because
(a) the electrons remain stationary
(b) the electrons are drifted in random direction with a speed of the order of 10^–2 cm/s
(c) the electrons move in random direction with a speed of the order close to that of velocity of light
(d) electrons and ions move in opposite direction.

Question. A meter bridge is used to determine the resistance of an unknown wire by measuring the balance point length l. If the wire is replaced by another wire of same material but with double the length and half the thickness, the balancing point becomes 2l, then the value of l is

Question. Twelve wires of each of resistance 6 W are connected to form a cube as shown in the figure. The current enters at a corner A and leaves at the diagonally opposite corner G. The joint resistance across the corners A and G is

(a) 12 Ω
(b) 6 Ω
(c) 3 Ω
(d) 5 Ω

Question. The temperature coefficient of resistance of a wire is 0.00125/K. At 300 K, its resistance is 1 Ω. The resistance of the wire will be 2 Ω at
(a) 1154 K
(b) 1100 K
(c) 1400 K
(d) 1127 K

Question. A uniform copper wire of length 1 m and cross-sectional area 5 × 10^–7 m² carries a current of 1 A. Assuming that there are 8 × 10²⁸ free electron/m3 in copper, how long will an electron take to drift from one end of the wire to the other?
(a) 0.8 × 10³ s
(b) 1.6 × 10³ s
(c) 3.2 ×10³ s
(d) 6.4 × 10³ s

Question. If the total emf in a thermocouple is a parabolic function expressed as E = at + 1/2 bt², which of the following relation does not hold good?
(a) neutral temperature t_n = – a/b
(b) temperature of inversion, ti = −2a/b
(c) thermoelectric power P = a + bt
(d) t_n = a/b

Question. A conductor and a semiconductor are connected in parallel as shown in the figure. At a certain voltage both ammeters register the same current. If the voltage of the DC source is increased then the

(a) ammeter connected to the semiconductor will register higher current than the ammeter connected to the conductor
(b) ammeter connected to the conductor will register higher current than the ammeter connected to the semiconductor
(c) ammeters connected to both semiconductor and conductor will register the same current
(d) ammeters connected to both semiconductor and conductor will register no change in the current.

Question. The current i in the circuit (see figure) is

(a) (1/45) A
(b) (1/15) A
(c) (1/10) A
(d) (1/5) A

Question. In the circuit shown below, the key is pressed at time t = 0. Which of the following statement(s) is (are) true?

(a) The voltmeter display − 5V as soon as the key is pressed and displays + 5 V after a long time
(b) The voltmeter will display 0 V at time t = ln 2 seconds
(c) The current in the ammeter becomes 1/e of the initial value after 1 second
(d) The current in the ammeter becomes zero after a long time

Question. For the resistance network shown in the figure, choose the correct option(s).

(a) The current through PQ is zero
(b) I1 = 3A
(c) The potential at S is less than that at Q
(d) I2 = 2A

Question. One kilogram of water at 20°C is heated in an electric kettle whose heating element has a mean (temperature averaged) resistance of 20 Ω. The rms voltage in the mains is 200 V. Ignoring heat loss from the kettle, time taken for water to evaporate fully, is close to [Specific heat of water = 4200 J/(kg°C), Latent heat of water = 2260 kJ/kg]
(a) 16 min
(b) 22 min
(c) 3 min
(d) 10 min

Question. The resistive network shown below is connected to a DC source of 16 V. The power consumed by the network is 4 Ω. The value of R is

(a) 6 W
(b) 8 W
(c) 1 W
(d) 16 W

Question. Acell of internal resistance rdrives current through an external resistance R. The power delivered by the cell to the external resistance will be maximum when
(a) R = 2r
(b) R = r
(c) R = 0.001 r
(d) R = 1000 r

Question. Two electric bulbs rated at 25W, 220 V and 100W, 220 V are connected in series across a 220 V voltage source. If the 25 W and 100W bulbs draw powers P₁ and P₂ respectively, then
(a) P₁ = 16W, P₂ = 4 W
(b) P₁ = 4 W, P₂ = 6 W
(c) P₁ = 9W, P₂ = 16 W
(d) P₁ = 16W, P₂ = 9 W

Question. Two equal resistances when connected in series to a battery consume electric power of 60 W. If these resistances are now connected in parallel combination to the same battery, the electric power consumed will be
(a) 60 W
(b) 30 W
(c) 240 W
(d) 120 W

Question. A current of 2 mA was passed through an unknown resistor which dissipated a power of 4.4 W. Dissipated power when an ideal power supply of 11 V is connected across it is
(a) 11 x 10⁻⁴ W
(b) 11 x 10⁻⁵ W
(c) 11 x 10⁵ W
(d) 11 x 10⁻³ W

Question. Two bars of radius r and 2r are kept in contact as shown. An electric current I is passed through the bars. Which one of following is correct ?

(a) Heat produced in bar BC is 4 times the heat produced in bar AB
(b) Electric field in both halves is equal
(c) Current density across AB is double that of across BC
(d) Potential difference across AB is 4 times that of across BC

Question. The three resistances of equal value are arranged in the different combinations shown below. Arrange them in increasing order of power dissipation

(a) III < II < IV < I
(b) II < III < IV < I
(c) I < IV < III < II
(d) I < III < II < IV

Question. A 100 W bulb B₁, and two 60 W bulbs B₂ and B₃, are connected to a 250 V source, as shown in the figure. Now W₁ W₂, and W₃ are the output powers of the bulbs B₁ B₂, and B₃ respectively. Then,

(a) W₁ > W₂ = W₃
(b) W₁ > W₂ > W₃
(c) W₁ < W₂ = W₃
(d) W₁ < W₂ < W₃

Question. A wire of length L and 3 identical cells of negligible internal resistances are connected in series. Due to the current, the temperature of the wire is raised by DT in a time t. A number N of similar cells is now connected in series with a wire of the same material and cross-section but of length 2L. The temperature of the wire is raised by the same amount DT in the same time. The value of N is
(a) 4
(b) 6
(c) 8
(d) 9

Question. If we add impurity to a metal those atoms also deflect electrons. Therefore,
(a) the electrical and thermal conductivities both increase.
(b) the electrical and thermal conductivities both decrease.
(c) the electrical conductivity increases but thermal conductivity decreases.
(d) the electrical conductivity decreases but thermal conductivity increases.

Question. An ammeter and a voltmeter of resistance R are connected in series to an electric cell of negligible internal resistance. Their reading are A and V respectively. If another resistance R is connected in parallel with the voltmeter, then
(a) both A and V will increase.
(b) both A and V will decrease.
(c) A will decrease and V will increase.
(d) A will increase and V will decrease.

Question. Four resistances of 10 Ω, 60 Ω, 100 Ω and 200 Ω respectively taken in order are used to form a Wheatstone’s bridge. A 15 V battery is connected to the ends of a 200 W resistance, the current through it will be
(a) 7.5 × 10^–5 A
(b) 7.5 × 10^–4 A
(c) 7.5 × 10^–3 A
(d) 7.5 × 10^–2 A

Question. The potential difference across the terminals of a battery is 50 V when 11 A current is drawn and 60 V when 1 A current is drawn. The emf and the internal resistance of the battery are
(a) 62 V, 2 Ω
(b) 63 V, 1 Ω
(c) 61 V, 1 Ω
(d) 64 V, 2 Ω

Question. A battery is charged at a potential of 15 V in 8 h when the current flowing is 10 A. The battery on discharge supplies a current of 5 A for 15 h. The mean terminal voltage during discharge is 14 V. The watt-hour efficiency of the battery is
(a) 80%
(b) 90%
(c) 87.5%
(d) 82.5%

Question. In the Wheatstone’s network given, P = 10 Ω, Q = 20 Ω, R = 15 Ω, S = 30 Ω, the current passing through the battery (of negligible internal resistance) is

(a) 0.36 A
(b) zero
(c) 0.18 A
(d) 0.72 A

Question. In the circuit shown in figure the heat produced in the 5 W resistor due to the current flowing through it is 10 cal/s.

The heat generated in the 4 W resistor is
(a) 1 cal/s
(b) 2 cal/s
(c) 3 cal/s
(d) 4 cal/s

Question. A network of resistances, cell and capacitor C (= 2 μF) is shown in figure. In steady state condition, the charge on 2 μF capacitor is Q, while R is unknown resistance. Values of Q and R are respectively

(a) 4 μC and 10 Ω
(b) 4 μC and 4 Ω
(c) 2 μC and 2 Ω
(d) 8 μC and 4 Ω

Question. Seven resistances are connected between points A and B as shown in figure. The equivalent resistance between A and B is

(a) 5 Ω
(b) 4.5 Ω
(c) 4 Ω
(d) 3 Ω

Question. When a resistor of 11 Ω is connected in series with an electric cell, the current flowing in it is 0.5 A. Instead when a resistor of 5 Ω is connected to the same electric cell in series, the current increases by 0.4 A. The internal resistance of the cell is
(a) 1.5 Ω
(b) 2 Ω
(c) 2.5 Ω
(d) 3.5 Ω

Question. The magnitude and direction of the current in the circuit shown will be

(a) 7/3 A from a to b through e
(b) 7/3 A from b to a through e
(c) 1 A from b to a through e
(d) 1 A from a to b through e

Question. An electric bulb of 100 Ω is connected to a supply of electricity of 220 V. Resistance f the filament is
(a) 484 Ω
(b) 100 Ω
(c) 22000 Ω
(d) 242 Ω

Question. An incandescent bulb has a thin filament of tungsten that is heated to high temperature by passing an electric current. The hot filament emits black-body radiation. The filament is observed to break up at random locations after a sufficiently long time of operation due to non-uniform evaporation of tungsten from the filament. If the bulb is powered at constant voltage, which of the following statement(s) is (are) true?
(a) The temperature distribution over the filament is uniform.
(b) The resistance over small sections of the filament decreases with time.
(c) The filament emits more light at higher band of frequencies before it breaks up.
(d) The filament consumes less electrical power towards the end of the life of the bulb.

Question. For the circuit shown in the figure

(a) the current I through the battery is 7.5 mA
(b) the potential difference across RL is 18 V
(c) ratio of powers dissipated in R₁ and R₂ is 3
(d) if R₁ and R₂ are interchanged, magnitude of the power dissipated in RL will decrease by a factor of 9

Question. In a meter bridge experiment, the circuit diagram and the corresponding observation table are shown in figure

Which of the readings is inconsistent?
(a) 3
(b) 2
(c) 1
(d) 4

Question. In the circuit shown, a four-wire potentiometer is made of a 400 cm long wire, which extends between A and B. The resistance per unit length of the potentiometer wire is r = 0.01 W/cm. If an ideal voltmeter is connected as shown with jockey J at 50 cm from end A, the expected reading of the voltmeter will be  

(a) 0.20 V
(b) 0.75 V
(c) 0.25 V
(d) 0.50 V

Question. A galvanometer whose resistance is 50 W, has 25 divisions in it. When a current of 4 x 10⁻⁴ A passes through it, its needle (pointer) deflects by one division. To use this galvanometer as a voltmeter of range 2.5 V, it should be connected to a resistance of
(a) 250 Ω
(b) 6200 Ω
(c) 200 Ω
(d) 6250 Ω

Question. In a meter bridge, the wire of length 1m has a non-uniform cross-section such that the variation dR/dl of its resistance R with length l is dR/dl = 1/√l Two equal resistance are connected as shown in the figure. The galvanometer has zero deflection when the jockey is at point P. What is the length AP?
(a) 0.3 m
(b) 0.25 m
(c) 0.2 m
(d) 0.35 m

Question. An ideal battery of 4 V and resistance R are connected in series in the primary circuit of a potentiometer of length 1 m and resistance 5 Ω. The value of R to give a potential difference of 5 mV across 10 cm of potentiometer wire is
(a) 395 Ω
(b) 495 Ω
(c) 490 Ω
(d) 480 Ω

Question. The galvanometer deflection, when key K₁ is closed but K₂ is open equals θ₀ (see figure). On closing K₂ also and adjusting R₂ to 5 Ω, the deflection in galvanometer becomes θ₀/5. The resistance of the galvanometer is given by (neglect the internal resistance of battery) :

(a) 22W
(b) 5W
(c) 25W
(d) 12W

Question. In the experimental set up of meter bridge shown in the figure, the null point is obtained at a distance of 40 cm from A. If a 10 Ω resistor is connected in series with R₁, the null point shifts by 10 cm. The resistance that should be connected in parallel with (R₁ + 10) Ω such that the null point shifts back to its initial position is

(a) 60 Ω
(b) 20 Ω
(c) 30 Ω
(d) 40 Ω

Question. A galvanometer having a resistance of 20 Ω and 30 divisions on both sides has figure of merit .005 ampere/division. The resistance that should be connected in series such that it can be used as a voltmeter upto 15 volt is
(a) 100 Ω
(b) 125 Ω
(c) 120 Ω
(d) 80 Ω

Question. The resistance of the meter bridge AB in given figure is 4Ω. With a cell of emf e = 0 5 . V and rheostat resistance R_h = 2Ω. The null point is obtained at some point J. When the cell is replaced by another one of emf e = ∈₂, the same null point J is found for R_h = 6Ω. The emf ∈₂ is

(a) 0.6 V
(b) 0.3 V
(c) 0.5 V
(d) 0.4 V

Question. A potentiometer wire AB having length L and resistance 12r is joined to a cell D of EMF e and internal resistance r. A cell C having emf e/2 and internal resistance 3r is connected. The length AJ at which the galvanometer as shown in figure shows no deflection is

(a) (5/12) L
(b) (11/12) L
(c) (13/24) L
(d) (11/24) L

Question. A galvanometer having a coil resistance of 100 W gives a full scale deflection when a current of 1 mA is passed through it. The value of the resistance which can convert this galvanometer into ammeter giving a full scale deflection for a current of 10 A, is
(a) 0.01 Ω
(b) 2 Ω
(c) 0.1 Ω
(d) 3 Ω

Question. During an experiment with a meter bridge, the galvanometer shows a null point when the jockey is pressed at 40.0 cm using a standard resistance of 90 W, as show in the scale used in the meter bridge is 1 mm. The unknown resistance is

(a) 60 ± 0.15 Ω
(b) 135 ± 0.56 Ω
(c) 60 ± 0.25 Ω
(d) 135 ± 0.23 Ω

Question. A meter bridge is set-up as shown in figure, to determine an unknown resistance X using a standard 10 Ω resistor. The galvanometer shows null point when tapping-key is at 52 cm mark. The end-corrections are 1 cm and 2 cm respectively for the ends A and B. The determined value of X is

(a) 10.2 Ω
(b) 10.6 Ω
(c) 10.8 Ω
(d) 11.1 Ω

Question. A resistor of 6 kΩ with tolerance 10% and another resistor of 4 kΩ with tolerance 10% are connected in series. The tolerance of the combination is about
(a) 5%
(b) 10%
(c) 12%
(d) 15%

Question. In a hydrogen discharge tube, it is observed that through a given cross-section 3.31 × 10¹⁵ electrons are moving from right to left and 3.12 × 10⁵ protons are moving from left to right. The current in the discharge tube and its direction will be
(a) 2 mA, towards left
(b) 2 mA, towards right
(c) 1 mA, towards right
(d) 1 mA, towards left

Question. To verify Ohm’s law, a student is provided with a test resistor RT , a high resistance R₁, a small resistance R₂, two identical galvanometers G₁ and G₂, and a variable voltage source V. The correct circuit to carry out the experiment is

Question. A resistance of 2Ω is connected across one gap of a meter-bridge (the length of the wire is 100 cm) and an unknown resistance, greater than 2 Ω, is connected across the other gap. When these resistances are interchanged, the balance point shifts by 20 cm. Neglecting any corrections, the unknown resistance is
(a) 3 Ω
(b) 4 Ω
(c) 5 Ω
(d) 6 Ω

Question. A moving coil galvanometer of resistance 100 W is used as an ammeter using a resistance 0.1 Ω. The maximum deflection current in the galvanometer is 100μA. Find the current in the circuit, so that the ammeter shows maximum deflection.
(a) 100.1 mA
(b) 1000.1 mA
(c) 10.01 mA
(d) 1.01 mA

Question. For the post office box arrangement to determine the value of unknown resistance, the unknown resistance should be connected between

(a) B and C
(b) C and D
(c) A and D
(d) B1 and C₁

Question. In the shown arrangement of the experiment of the meter bridge if AC corresponding to null deflection of galvanometer is x, what would be its value if the radius of the wire AB is doubled ?

(a) x
(b) x/4
(c) 4x
(d) 2x

Question. Which of the following set-up can be used to verify Ohm’s law ?

Mark your answer as
(a) If Statement I is true, Statement II is true; Statement II is the correct explanation for Statement I
(b) If Statement I is true, Statement II is true; Statement II is not a correct explanation for Statement I
(c) If Statement I is true; Statement II is false
(d) If Statement I is false; Statement II is true

Question. Consider two identical galvanometers and two identical resistors with resistance R. If the internal resistance of the galvanometers R₂ < R/2, which of the following statement (s) about anyone of the galvanometers is (are) true?
(a) The maximum voltage range is obtained when all the components are connected in series
(b) The maximum voltage range is obtained when the two resistors and one galvanometer are connected in series, and the second galvanometer is connected in parallel to the first galvanometer
(c) The maximum current range is obtained when all the components are connected in parallel
(d) The maximum current range is obtained when the two galvanometers are connected in series, and the combination is connected in parallel with both the resistors

Question. A microammeter has a resistance of 100 Ω and full scale range of 50μA. It can be used as a voltmeter or as a higher range ammeter provided a resistance is added to it. Pick the correct range and resistance combination (s)
(a) 50 V range with 10 k Ω resistance in series
(b) 10 V range with 200 k Ω resistance in series
(c) 5 mA range with 1 Ω resistance in parallel
(d) 10 mA range with 1 Ω resistance in parallel

Question. A thin uniform wire AB of length 1 m, an unknown resistance X and a resistance of 12 Ω are connected by thick conducting strips, as shown in the figure. A battery and galvanometer (with a sliding jockey connected to it are also available). Connections are to be made to measure the unknown resistance X using the principle of Wheatstone bridge. Answer the following questions.

(a) Are there positive and negative terminals on the galvanometer?
(b) Copy the figure in your answer book and show the battery and the galvanometer (with jockey) connected at appropriate points.
(c) After appropriate connections are made, it is found that no deflection takes place in the galvanometer when the sliding jockey touches the wire at a distance of 60 cm from A. Obtain the value of the resistance X.

Question. A 200 W resistor has a certain colour code. If one replaces the red colour by green in the code, the new resistance will be
(a) 100 Ω
(b) 400 Ω
(c) 300 Ω
(d) 500 Ω

Question. The Wheatstone bridge shown in figure here, gets balanced when the carbon resistor is used as R₁ has the color code (orange, red, brown). The resistors R₂ and R₄ are 80Ω and 40 Ω, respectively. Assuming that the color code for the carbon resistors gives their accurate values, the color code for the carbon resistor is used as R₃ would be

(a) brown, blue, black
(b) brown, blue, brown
(c) grey, black, brown
(d) red, green, brown

Question. The actual value of resistance R , shown in the figure is 30 W. This is measured in an experiment as shown using the standard formula R = V/I, where V and I are the readings of the voltmeter and ammeter, respectively. If the measured value of R is 5% less, then the internal resistance of the voltmeter is

(a) 600 Ω
(b) 570 Ω
(c) 350 Ω
(d) 35 Ω

Question. A 2 W carbon resistor is color coded with green, black, red and brown respectively. The maximum current which can be passed through this resistor is
(a) 0.4 mA
(b) 63 mA
(c) 20 mA
(d) 100 mA

Question. A resistance is shown in the figure. Its value and tolerance are given respectively by

(a) 270 Ω, 5%
(b) 27 k Ω, 20%
(c) 27 k Ω, 10%
(d) 270 k Ω, 10%

Question. A carbon resistance has a following color code. What is the value of the resistance?

(a) 5.3MΩ ± 5%
(b) 64 kΩ ± 10%
(c) 6.4 MΩ ± 5%
(d) 530 kΩ ± 5%

Question. In candescent bulbs are designed by keeping in mind that the resistance of their filament increases with the increase in temperature. If at room temperature, 100 W, 60Wand 40W bulbs have filament resistances R100 R60 , and R40, respectively, the relation between these resistances is

Question. Figure shows three resistor configurations R₁, R₂ and R₃ connected to 3 V battery. If the power dissipated by the configuration R₁, R₂ and R₃ is P₁, P₂ and P₃, respectively, then

(a) P₁ > P₂ > P₃
(b) P₁ > P₃ > P₂
(c) P₂ > P₁ > P₃
(d) P₃ > P₂ > P₁

Question. A rigid container with thermally insulated walls contains a coil of resistance 100 Ω, carrying current 1 A. Change in internal energy after 5 min will be
(a) zero
(b) 10 kJ
(c) 20 kJ
(d) 30 kJ

Assertion-Reason Questions

In the following questions, a statement of Assertion (A) is followed by a statement of Reason (R). Choose the correct answer out of the following choices.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false and R is also false.

Question. Assertion (A): The current density is a vector quantity.
Reason (R): Current density has magnitude current per unit area and is directed along the direction of current.

Question. Assertion (A): The current flows in a conductor when there is an electric field within the conductor.
Reason (R): The electrons in a conductor drift only in the presence of electric field.

Question. Assertion (A): The drift velocity of electrons in a metallic conductor decreases with rise of temperature of conductor.
Reason (R): On increasing temperature, the collision of electrons with lattice ions increases; this hinders the drift of electrons.

Question. Assertion (A): Electric current is a scalar quantity.
Reason (R): Electric current arises due to continuous flow of charged particles.

Question. Assertion (A): The resistance of a given mass of copper wire is inversely proportional to the square of length.
Reason (R): When a copper wire of given mass is stretched to increase its length, its crosssectional area also increases.

Question. Assertion (A): A domestic electric appliance, working on a three pin, will continue working even if the top pin is removed.
Reason (R): The second pin is used as a safety device.

Question. Assertion (A): The connecting wires are made of copper.
Reason (R): Copper has very high electrical conductivity.

Question. Assertion (A): With increase in drift velocity, the current flowing through a metallic conductor decreases.
Reason (R): The current flowing in a conductor is inversely proportional to drift velocity.

Question. Assertion (A): In series combination of 200 W, 100 W and 25 W bulbs, the bulb of 200 W bulb shines most brightly.
Reason (R): 25 W has minimum resistance and so p.d. across it is maximum.

Question. Assertion (A): Material used in construction of a standard resistance is constantan.
Reason (R): The temperature coefficient of resistance of constantan is negligible.

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