JEE Physics Current Electricity MCQs Set 03

Question. The potentiometer is best for measuring voltage as
(a) It measures p.d in open circuit
(b) It has wire of high resistance
(c) It has a sensitive galvanometer
(d) It measures p.d. in closed circuit

Answer: A

Question. The resistance of each arm of the Wheatstone’s bridge is 10 ohm. A resistance of 10 ohm is connected in series with a galvanometer then the equivalent resistance across the battery will be
(a) 10 ohm
(b) 15 ohm
(c) 20 ohm
(d) 40 ohm

Answer: A

Question. Copper and silicon are cooled from 300 K to 60 K, the specific resistance
(a) 10 ohm
(b) 15 ohm
(c) 20 ohm
(d) 40 ohm

Answer: A

Question. Copper and silicon are cooled from 300 K to 60 K, the specific resistance
(a) Decreases in copper but increases in silicon
(b) Increases in copper but decreases in silicon
(c) Decreases in both
(d) Increases in both

Answer: A

Question. Specific resistance of a conductor increases with
(a) Increase in temperature
(b) Increase in cross-sectional area
(c) Decrease in cross-sectional area
(d) Increase in cross-sectional and decrease in length

Answer: A

Question. In a Wheatstone’s bridge all the four arms have equal resistance R. If the resistance of the galvanometer arm is also R, the equivalent resistance of the combination as seen by the battery is
(a) R
(b) 2R
(c) R/2
(d) R/4

Answer: A

Question. The electric resistance of a certain wire of iron is R. If its length and radius are both doubled, then
(a) The resistance will be halved and the specific resistance will remain uncharged
(b) The resistance will be doubled and the specific resistance will be halved
(c) The resistance will be halved and the specific resistance will he doubled
(d) The resistance and the specific resistance, will both remain unchanged

Answer: A

Question. The resistances of the four arms P, Q, R and S in a Wheatstone's bridge are 10 ohm, 30 ohm, 30 ohm and 90 ohm, respectively. The e.m.f. and internal resistance of the cell are 7 volt and 5 ohm respectively. If the galvanometer resistance is 50 ohm, the current drawn from the cell will be
(a) 0.2 A
(b) 0.1 A
(c) 2.0 A
(d) 1.0 A

Answer: A

Question. A 6 volt battery is connected to the terminals of a three metre long wire of uniform thickness and resistance of 100 ohm. The difference of potential between two points on the wire separated by a distance of 50 cm will be
(a) 1 volt
(b) 1.5 volt
(c) 3 volt
(d) 2 volt

Answer: A

Question. Kirchhoff’s first and second laws of electrical circuits are consequences of
(a) Conservation of electric charge and energy respectively
(b) Conservation of electric charge
(c) Conservation of energy
(d) Conservation of energy and electric charge respectively

Answer: B

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  0°C? The temperature of boiling water is 100°C.
(a) 6.3 min
(b) 8.4 min
(c) 12.6 min
(d) 4.2 min

Answer: A

Question. A heating coil is labelled 100 W, 220 V. The coil is cut in half and the two pieces are joined in parallel to the same source. The energy now liberated per second is
(a) 400 J
(b) 25 J
(c) 50 J
(d) 200 J

Answer: A

Question. A (100 W, 200 V) bulb is connected to a 160 volt supply. The power consumption would be
(a) 64 W
(b) 80 W
(c) 125 W
(d) 100 W

Answer: A

Question. If two bulbs, whose resistances are in the ratio of 1 : 2 are connected in series, the power dissipated in them has the ratio of
(a) 1 : 2
(b) 1 : 1
(c) 1 : 4
(d) 2 : 1

Answer: A

Question. Two 220 volt, 100 watt bulbs are connected first in series and then in parallel. Each time the combination is connected to a 220 volt a.c. supply line. The power drawn by the combination in each case respectively will be
(a) 50 watt, 200 watt
(b) 200 watt, 150 watt
(c) 100 watt, 50 watt
(d) 50 watt, 100 watt

Answer: A

Question. An electric kettle has two heating coils. When one of the coils is connected to an a.c. source, the water in the kettle boils in 10 minute. When the other coil is used the water boils in 40 minute. If both the coils are connected in parallel, the time taken by the same quantity of water to boil will be
(a) 8 minute
(b) 4 minute
(c) 25 minute
(d) 15 minute

Answer: A

Question. Fuse wire is a wire of
(a) Low resistance and low melting point
(b) High resistance and high melting point
(c) High resistance and low melting point
(d) Low resistance and high melting point

Answer: A

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

Answer: A

Question. When three identical bulbs of 60 watt, 200 volt rating are connected in series to a 200 volt supply, the power drawn by them will be
(a) 20 watt
(b) 10 watt
(c) 180 watt
(d) 60 watt

Answer: A

Question. A 5-ampere fuse wire can withstand a maximum power of 1 watt in the circuit. The resistance of the fuse wire is
(a) 0.04 ohm
(b) 0.2 ohm
(c) 5 ohm
(d) 0.4 ohm

Answer: A

Question. Consider the following two statements
(A) Kirchhoff's junction law follows from the conservation of charge.
(B) Kirchhoff's loop law follows from the conservation of energy.
Which of the following is correct?
(a) Both (A) and (B) are correct
(b) Both (A) and (B) are wrong
(c) (A) is wrong and (B) is correct
(d) (A) is correct and (B) is wrong

Answer: A