Current Electricity MCQ Questions with Answers Class 12 Physics Chapter 3
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 the electric mains is 220 V. The minimum capacity of the main fuse of the building will be :
(a) 10 A
(b) 12 A
(c) 14 A
(d) 8 A
Ans-(b)
Question- This question has Statement-I and Statement-II. Of the four choices given after the statements, choose the one that best describes the two Statements.
Statement-I : Higher the range, greater is the resistance of ammeter.
Statement-II : To increase the range of ammeter, additional shunt needs to be used across it.
(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 if false; Statement-Ii is true.
Ans-(d)
Question- The supply voltage in a room is 120 V. The resistance of the lead wires is 6Ω. 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) 10.04 V
Ans-(d)
Question- Two electric bulbs marked 25 W–220 V and 100 W-220 V are connected in series to a 440 V supply. Which of the bulbs will fuse ?
(a) Both
(b) 100 W
(c) 25 W
(d) Neither
Ans-(c)
Question- Resistance of a given wire is obtained by measuring the current flowing in it and the voltage difference applied across it. If the percentage errors in the measurement of the current and the voltage difference are 3% each, then error in the value of resistance of the wire is
(a) 6%
(b) zero
(c) 1%
(d) 3%
Ans-(a)
Question- The resistance of a wire is 5 Ω at 50°C and 6 Ω at 100°C.The resistance of the wire at 0°C will be
(a) 2 Ω
(b) 1 Ω
(c) 4 Ω
(d) 3 Ω
Ans-(c)
Question- A material B has twice the specific resistance of A. A circular wire made of B has twice the diameter of a wire made of A. Then for the two wires to have the same resistance, the ratio B/A of their respective lengths must be
(a) 1
(b) 1/2
(c) 1/4
(d) 2
Ans-(d)
Question- An electric bulb is rated 220 V-100 W. The power consumed by it when operated on 110 V will be
(a) 75 W
(b) 40 W
(c) 25 W
(d) 50 W
Ans-(c)
Question- The resistance of a bulb filament is 100 Ω at a temperature of 100°C. If its temperature coefficient of resistance be 0.005 per °C, its resistance will become 200 Ω at a temperature of
(a) 300°C
(b) 400°C
(c) 500°C
(d) 200°C
Ans-(a)
Question- A heater coil is cut into two equal parts and only one part is now used in the heater. The heat generated will now be
(a) doubled
(b) four times
(c) one-fourth
(d) halved
Ans-(a)
Question- An energy source will supply a constant current into the load, if its internal resistance is
(a) equal to the resistance of the load
(b) very large as compared to the load resistance
(c) zero
(d) non-zero but less than the resistance of the load
Ans-(c)
Question- In a potentiometer experiment the balancing with a cell is at length 240 cm. On shunting the cell with a resistance of 2 Ω, the balancing length becomes 120 cm. The internal resistance of the cell is
(a) 1 Ω
(b) 0.5 Ω
(c) 4 Ω
(d) 2 Ω
Ans-(d)
Question- The resistance of hot tungsten filament is about 10 times the cold resistance. What will be the resistance of 100 W and 200 V lamp, when not in use ?
(a) 40 Ω
(b) 20 Ω
(c) 400 Ω
(d) 200 Ω
Ans-(a)
Question- The resistance of the series combination of two resistances is S. When they are joined in parallel, the total resistance is P. If S = nP, then the minimum possible value of n is
(a) 4
(b) 3
(c) 2
(d) 1
Ans-(a)
Question- In a meter bridge experiment, null point is obtained at 20 cm from one end of the wire when resistance X is balanced against another resistance Y. If X < Y, then where will be the new position of the null point from the same end, if one decides to balance a resistance of 4X against Y ?
(a) 50 cm
(b) 80 cm
(c) 40 cm
(d) 70 cm
Ans-(a)
Question- Time taken by a 836 W heater to heat one litre of water from 10°C to 40°C is
(a) 50 s
(b) 100 s
(c) 150 s
(d) 200 s
Ans-(c)
Question- The length of a given cylindrical wire is increased by 100%.Due to the consequent decrease in diameter the change in the resistance of the wire will be (AIEEE 2003)
(a) 200%
(b) 100%
(c) 50%
(d) 300%
Ans-(d)
Question- A 220 V, 1000 W bulb is connected across a 110 V mains supply. The power consumed will be
(a) 750 W
(b) 500 W
(c) 250 W
(d) 1000 W
Ans-(c)
Question- A wire when connected to 220 V mains supply has power dissipation P1. Now the wire is cut into two equal pieces which are connected in parallel to the same supply. Power dissipation in this case is P2. Then P2 : P1 is
(a) 1
(b) 4
(c) 2
(d) 3
Ans-(b)
Question- Current of 4.8 amperes is flowing through a conductor.The number of electrons crossing a cross-section per second will be
(a) 3 × 1019
(b) 7.68 × 1021
(c) 7.68 × 1020
(d) 3 × 1020
Ans-(a)
Question- An ionization chamber with parallel conducting plates as anode and cathode has 5 × 107 electrons and the same number of singly-charged positive ions per cm3. The electrons are moving at 0.4 m/s. The current density from anode to cathode is 4 μA/m2. The velocity of positive ions moving towards cathode is
(a) 0.4 m/s
(b) 16 m/s
(c) Zero
(d) 0.1 m/s
Ans-(d)
Question- The resistance of a galvanometer is 10 ohm. It gives full scale deflection when 1 mA current is passed. The resistance to be connected in series for converting it into a voltmeter of 2.5 volt will be
(a) 249 Ω
(b) 2490 Ω
(c) 299 Ω
(d) 2999 Ω
Ans-(b)
Question- A galvanometer has a resistance of 30 ohm and a current of 2 mA is needed to give full scale deflection. What is the resistance needed to convert it into a voltmeter of 0.2 volt range.
(a) 20 Ω
(b) 30 Ω
(c) 60 Ω
(d) 70 Ω
Ans-(d)
Please click on below link to download CBSE Class 12 Physics Current Electricity Worksheet Set D
