NEET Physics Current Electricity MCQs Set A

Question. Consider a current carrying wire (current I) in the shape of a circle.
(a) electric field produced by charges accumulated on the surface of wire
(b) the charges just behind a given segment of wire which push them just the right way by repulsion
(c) the charges ahead
(d) source of emf

Answer: A

Question. Two cells of emfs approximately 5 V and 10 V are to be accurately compared using a potentiometer of length 400 cm
(a) The battery of potentiometer can have a voltage of 15 V and R adjusted so that the potential drop across the wire slightly exceeds 10 V.
(b) The first portion of 50 cm of wire itself should have a potential drop of 10 V.
(c) Potentiometer is usually used for comparing resistances and not voltages
(d) The battery that runs the potentiometer should have voltage of 8V

Answer: A

Question. Which of the following characteristics of electrons determines the current in a conductor?
(a) Drift velocity alone
(b) Thermal velocity alone
(c) Both drift velocity and thermal velocity
(d) Neither drift nor thermal velocity

Answer: A

Question. The cold junction of a thermocouple is maintained at 10ºC. No thermo e.m.f. is developed when the hot junction is maintained at 530ºC. The neutral temperature is
(a) 270ºC
(b) 260ºC
(c) 265ºC
(d) 520ºC

Answer: A

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

Answer: A

Question. Assertion : When current through a bulb decreases by 0.5%, the glow of bulb decreases by 1%.
Reason : Glow (Power) which is directly proportional to square of current.
(a) If both Assertion and Reason are correct and Reason is the correct explanation of Assertion
(b) If both Assertion and Reason are correct, but Reason is not the correct explanation of Assertion
(c) If Assertion is correct but Reason is incorrect
(d) If both the Assertion and Reason are incorrect

Answer: A

Question. A constant voltage is applied between the two ends of a uniform metallic wire. Some heat is developed in it. The heat developed is doubled if
(a) both the length and the radius of the wire are doubled
(b) the radius of the wire is doubled
(c) the length of the wire is doubled.
(d) both the length and the radius of the wire are halved

Answer: A

Question. A potentiometer wire is 100 cm long and a constant potential difference is maintained across it. Two cells are connected in series first to support one another and then in opposite direction. The balance points are obtained at 50 cm and 10 cm from the positive end of the wire in the two cases. The ratio of emf's is :
(a) 3 : 2
(b) 3 : 4
(c) 5 : 4
(d) 5 : 1

Answer: A

Question. Assertion : Bending a wire does not effect electrical resistance.
Reason : Resistance of wire is proportional ot resistivity of material
(a) If both Assertion and Reason are correct and Reason is the correct explanation of Assertion
(b) If both Assertion and Reason are correct, but Reason is not the correct explanation of Assertion.
(c) If Assertion is correct but Reason is incorrect
(d) If both the Assertion and Reason are incorrect

Answer: A

Question. A potentiometer is an accurate and versatile device to make electrical measurements of E.M.F. because the method involves
(a) A condition of no current flow through the galvanometer
(b) A combination of cells, galvanometer and resistances
(c) Cells
(d) Potential gradients

Answer: A

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) Wheatstone bridge is the most sensitive when all the four resistances are of the same order of magnitude
(c) Kirchhoff's second law represents energy conservation
(d) A rheostat can be used as a potential divider

Answer: A

Question. A set of 'n' equal resistors, of value 'R' each,are connected in series to a battery of emf 'E' and internal resistance 'R'. The current drawn is I. Now, the 'n' resistors are connected in parallel to the same battery. Then the current drawn from battery becomes 10 I. The value of'n' is
(a) 10
(b) 11
(c) 9
(d) 20

Answer: A

Question. Assertion : A current flows in a conductor only when thereis an electric field within the conductor.
Reason : The drift velocity of electron in presence of electric field decreases.
(a) Assertion is correct, reason is incorrect
(b) Assertion is incorrect, reason is correct
(c) Assertion is correct, reason is correct; reason is not a correct explanation for assertion
(d) Assertion is correct, reason is correct; reason is a correct explanation for assertion.

Answer: A

Question. Ten identical cells connected in series are needed to heat a wire of length one meter and radius ‘r’ by 10ºC in time ‘t’. How many cells will be required to heat the wire of length two meter of the same radius by the same temperature in time ‘t’?
(a) 20
(b) 30
(c) 40
(d) 10

Answer: A

Question.  An electric heating element in vacuum is surrounded by a cavity at constant temperature of 227ºC; it consumes 60W of power to maintain a temperature of 727ºC. What is the power consumed by the element to maintain a temperature of 1227º C?
(a) 320 W
(b) 90 W
(c) 304 W
(d) 101 W

Answer: A

Question. An electrical cable of copper has just one wire of radius 9 mm. Its resistance is 5 ohm. This single copper wire of the cable is replaced by 6 different well insulated copper wires each of radius 3 mm. The total resistance of the cable will now be equal to
(a) 7.5 ohm
(b) 45 ohm
(c) 270 ohm
(d) 90 ohm

Answer: A

Question.  A hank of uninsulated wire consisting of seven and a half turns is stretched between two nails hammered into a board to which the ends of the wire are fixed. The resistance of the circuit between the nails is determined with the help of electrical measuring instruments. Determine the proportion in which the resistance will change if the wire is unwound so that the ends remain to be fixed to the nails.
(a) 225
(b) 15
(c) 240
(d) 250

Answer: A

Question. To get maximum current in a resistance of 3 ohms, one can use n rows of m cells (connected in series) connected in parallel. If the total number of cells is 24 and the internal resistance of a cell is 0.5 ohms then
(a) m = 12, n = 2
(b) m = 2, n = 12
(c) m = 8, n = 3
(d) m = 6, n = 4

Answer: A