JEE Physics Current Electricity MCQs Set D

Question. A 10 m long potentiometer wire is connected to a battery having a steady voltage. A Leclanche cell is balanced at 4 m length of the wire. If the length is kept the same, but its cross-section is doubled, the null point will be obtained at
(a) 4 m
(b) 2 m
(c) None of these
(d) 8 m

Answer: A

Question. Of the two bulbs in a house hold circuit, one glows brighter than the other, Which of the two bulbs has a large resistance?
(a) The dim bulb
(b) The bright bulb
(c) Both have the same resistance
(d) The brightness does not depend upon the resistance

Answer: A

Question. Two electric bulbs whose resistance are in the ratio of 1 : 2, are connected in parallel to a constant voltage source. The power dissipated in them has the ratio
(a) 2 : 1
(b) 1 : 1
(c) 1 : 4
(d) 1 : 2

Answer: A

Question. The same mass of aluminium is drawn into two wires 1 mm and 2 mm thick. Two wires are connected in series and current is passed through them. Heat produced in the wire is in the ratio
(a) 16 : 1
(b) 8 : 32
(c) 8 : 2
(d) 4 : 2

Answer: A

Question. How many 60 W bulbs may be safely run on 220 V using a 5 A fuse?
(a) 18
(b) 16
(c) 14
(d) 12

Answer: A

Question. A 50 W bulb connected in series with a heater coil is put to an AC mains. Now the bulb is replaced by a 100 W bulb. The heater output will
(a) Increase
(b) Decrease
(c) Halve
(d) Double

Answer: A

Question. Four equal resistance dissipated 5 W of power together when connected in series to a battery of negligible internal resistance. The total power dissipated in these resistance when connected in parallel across the same battery would be 
(a) 80 W
(b) 125 W
(c) 20 W
(d) 5 W

Answer: A

Question. Two heater coils separately take 10 minute and 5 minute to boil certain amount of water. If both the coils are connected in series, the time taken will be
(a) 15 min
(b) 7.5 min
(c) 3.33 min
(d) 2.5 min

Answer: A

Question. Select the correct statement
(a) Resistance is the opposition to the flow of current
(b) Resistivity of a conductor decreases with increase in temperature
(c) Electric current is a vector quantity
(d) Current density is a scalar quantity

Answer: A

Question. A current of 10 A is maintained in a conductor of cross-section 1 cm². If the free electron density in the conductor is 9 × 10²⁸ m^–3, then drift velocity of free electrons is
(a) 6.94 × 10^–6 m/s
(b) 5.94 × 10^–2 m/s
(c) 1.94 × 10^–3 m/s
(d) 2.94 × 10^–4 m/s

Answer: A

Question. Ten 60 W, 220 V bulbs are connected in series to 220 V supply. Power consumed in the circuit is
(a) 6 W
(b) 12 W
(c) 180 W
(d) 600 W

Answer: A