# MCQ of Current Electricity | Chapter 3 | Physics | Class 12 | CBSE |

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MCQ of Current Electricity, Chapter 3, Class 12, Physics

Question 1: The electrical resistance of a conductor depends upon

1. Size of conductor
2. Size of conductor
3. Geometry of conductor
4. All of these

Answer  :  D ( All of these )

Question 2:Electromotive force is able to maintain  a constant

1. Current
2. Resistance
3. Power
4. Potential difference

Answer  :  D ( Potential Difference )

Question 3:When a metal conductor connected to left gap of a meter bridge is heated, the balancing point

1. Shifts towards right
2.  Shifts towards left
3. Remains unchanged
4. Remains at zero

Answer  :  A ( Shifts towards right )

Question 4: In a wheat stone bridge if the battery and galvanometer are interchanged then what will be affect on the galvanometer deflection

1. Change in previous direction
2. Not change
3. Change in opposite direction.
4. None of these.

Answer  : B ( not change )

Question 5:In series combination of n cells, we obtain

1. More voltage
2. More current
3. Less voltage
4. Less current

Answer : B ( More voltage )

Question 6:Which statement is correct about the validity of Kirchhoff’s loop rule

1. It lies on conservation of charge.
2. Departing currents add up and are equal to incoming currents at a junction.
3. Flexing or reorienting the wire does not change the validity of Kirchhoff’s junction rule.
4. All of these

Answer : D ( All of these )

Question 7:Choose the correct dimensional formula of resistance

1. [MLT-3A-2]
2. [MLT-1A-3]
3. [ML1 T-3A-2]
4. [MLT-3A-1]

Answer  : A ( [MLT-3A-2] )

Question 8:A negative charge is moving via junction, then

1. Momentum will be conserved.
2. Momentum will not be conserved.
3. At some places momentum will be conserved and at some other places momentum will not be conserved , it depends on place where the charge is placed
4. None of these.

Answer  D : ( None of these )

Question 9: Match the column as follows

 Column I Column 2 A Ohm’s Law is valid to- P -metals B Ohm’s law is not valid to- Q -greater resistivity C alloys have- R -diodes and semiconductors
1. A-R , B-R , C-R
2. A-P , B-R , C-Q
3. A-R , B-P , C-Q
4. A-Q , B-R , C-P

Answer  : B ( A-P , B-R , C-Q )

Question 10:In a potentiometer furnished with 20 wires, the balance point is acquired on the 17th wire. To shift the balance point to 19th wire, we should do as follows

1. Should decrease resistance of the main circuit.
2. Should increase resistance of the main circuit.
3. Should decrease resistance in series with the cell whose EMF is to be find out.
4. Should increase resistance in series with the cell whose EMF is to be find out.

Answer  : D ( Increase resistance in series with the cell whose EMF is to be find out. )

You may also read MCQ of Electric Charges and Fields, MCQ of Electrostatic Potential and Capacitance, MCQ of Moving Charges and Magnetism, MCQ of Magnetism and Matter, MCQ of Electromagnetic Induction, MCQ of Alternating Current for better understanding of the chapters.

Question 11:(A). Current flows in a conductor only when there is an external electric field applied to the conductor.

(B).The drift velocity of electrons is directly proportional to the electric field.

1. Only A is correct
2. Only B is correct
3. Both A & B are correct
4. Both A and b are false

Answer : C ( Both A & B are correct )

Question 12:What is the value of unknown resistance R, if galvanometer shows null deflection in the given meter bridge set up? 1. 97.50 Ω
2. 105 Ω
3. 150 Ω
4. 110 Ω

Answer  : A ( 97.50 Ω )

Question 13:If you have a positive charge ,what conclusion can be drawn about current density?

1. Direction of current and current density is opposite
2. Direction of current and current density is same
3. Current density and current are independent
4. direction can not be determined

Answer : B ( Direction of current and current density is same )

Question 14:Specify the value of resistance if carbon code is

Green – Brown – Yellow – Gold

1. 50 X 104 ± 4%
2. 51 X 104 ± 5%
3. 47 X 103 ± 2%
4. 32 X 105 ± 5%

Answer  : B ( 50 X 104 ± 5% )

Ques 15:Which is correct expression for microscopic form of ohm’s law

1. E=J.ρ
2. J=E.σ
3. E=ρ.I/A
4. All of the above

Answer : D ( All of the above )

Question 16: Specify the relation between EMF of a cell and external resistance

1. EMF of a cell depends directly on external resistance
2. EMF of a cell depends directly on external resistance
3. EMF of a cell is independent of external resistance
4. EMF of a cell first increases and then decreases with external resistance

Answer  : C ( EMF of a cell is independent of external resistance )

Question 17:When the cells are connected in mixed grouping

1. High EMF is obtained
2. High current is obtained
3. High power is obtained
4. None of these

Answer  : C ( High power is obtained )

Question 18: In series combination of n cells , having an EMF ‘E’ and internal resistance ‘r’ . If 3 cells are wrongly connected, what will be the total EMF and internal resistance

1. EMF= n*E;  r=6Ω
2. EMF= nE-6E;  r=independent
3. EMF=independent ;  r=1Ω
4. EMF= n/6E;  r=independent

Question 19:Which of the following is not an application of wheat stone bridge

1. To find unknown resistance
2. To find specific resistance
3. To compare EMF of two cells
4. To verify resistance whether in series or parallel combination

Answer : C ( To compare EMF of two cells )

Question 20:Wheat stone bridge can be used to determine ________value of resistors?

1. High value only
2. Low value only
3. Moderate Value only
4. All of the above

Answer : C ( Moderate value only )

Question 21: Which of the following is an application of potentiometer

1. To measure potential drop of a certain section
2. To compare the EMF of two cells
3. To find internal resistance of a cell
4. All of the above

Answer :  D( All of these )

Question 22: EMF of a cell is less than the terminal potential difference when

1. Charging condition
2. Always
3. Discharging condition
4. Never

Answer : A ( Charging condition )

Question 23:In a combination on ‘n ‘cells , if the polarity of ‘m’ cells is reversed,

1. E eq=n E
2. E eq=(n-2 m)E
3. E eq=(n-2 m)/E
4. E eq=(n+2 m)/E

Answer  : B ( E eq=(n-2 m)E )

Question 24: Ramesh has 12 old cells . He needs maximum output out of these, in which of the following combinations ,he must connect the respective cells

1. Cells should be connected in series combination
2. Cells should be connected in parallel combination
3. Cells should be connected in mixed grouping
4. Nothing can be done

Answer : B ( Cells should be connected in parallel combination )

Question 25:Which of the following is correct about temperature coefficient of metals and alloys

1. (Temperature coefficient of metals)>(temperature coefficient of alloys)
2. (Temperature coefficient of alloys)>(temperature coefficient of alloys)
3. Temperature coefficient of metals is nearly equal to temperature coefficient of alloys
4. (Temperature coefficient of alloys)<=(temperature coefficient of alloys)

Answer : A ( (Temperature coefficient of metals)>(temperature coefficient of alloys) )

Question 26: Which of the following must be constant for the validity of Ohm’s Law

1. Temperature
2. Pressure
3. Mechanical strain
4. All of these

Answer  : D ( All of these )

Question 27:Why standard resistors are made up of alloys (specifically manganin and constantan)

1. These alloys have high temperature coefficients
2. These alloys have low temperature coefficients
3. These alloys have high resistivity
4. Both B & C

Answer  : D ( Both B and C )

Question 28:How does relaxation time and temperature related to each other

1. Relaxation time varies inversely with temperature
2. Relaxation time varies directly with temperature
3. Relaxation time is independent of temperature
4. Relaxation time first increases and then decreases with temperature

Answer  : A( Relaxation time varies inversely with temperature )

Question 29:What is the direction of  electronic current?

1. Positive to negative
2. Negative to positive
3. Undefined
4. Parallel to electric field

Answer : B ( Negative to positive )

Question 30:How the values of magnitude and direction varies with time for steady direct current?

1. Magnitude changes with time ;direction remains unchanged
2. Magnitude remains unchanged ; direction changes with time
3. Magnitude changes with time ; direction also changes with time
4. Magnitude remains unchanged ; direction also remains unchanged

Answer : D ( Magnitude remains unchanged ; direction also remains unchanged )

Question 31:A boy has two spare light bulbs in his drawer. One is marked 240 V and 100 W and the other is marked 240 V and 60 W. He tries to decide which of the following assertions are correct?

1. The 60 W light bulb has more resistance and therefore burns less brightly.
2. The 60 W light bulb has less resistance and therefore burns less brightly.
3. The 100 W bulb has more resistance and therefore burns more brightly.
4. The 100 W bulb has less resistance and therefore burns less brightly.

Answer : A ( The 60 W light bulb has more resistance and therefore burns less brightly. )

Question 32: The resistance of the wire in platinum resistance thermometer at ice point is 5Ω and at steam point is 5.25Ω .When the thermometer is inserted in an unknown hot bath its resistance is found yo be 5.5Ω.The temperature of hot bath is

1. 100°C
2. 200°C
3. 300°C
4. 350 °C

Answer : B ( 200°C )

Question 33: A battery , an open circuit and a resistor are connected in series . Consider the following 3 statements concerning the circuit . A voltmeter will read zero if it is connected across points

(i)P and T

(ii)P and Q

(iii)Q and T

Which one of the above is/are true?

1. Only(i)
2. only (iii)
3. Only(i and iii)
4. (i),(ii) and 9(iii)

Answer  : C ( Only(i and iii) )

Question 34:The resistivity of alloy manganin is

1. Nearly independent of temperature
2. Increase rapidly with increase in temperature
3. Decrease rapidly with increase in temperature
4. Increase rapidly with decrease in temperature

Answer A : ( Nearly independent of temperature )

Question 35: The correct combination of three resistance 1Ω,2Ω and 3Ω to equivalent resistance 11/5Ω is

1. All three are combined in parallel
2. All three are combined in series
3. 1Ω and 2Ω in parallel and 3Ω in series to both
4. 2Ω and 3Ω are combined in parallel and 1 Ω is in series to both

Answer : D ( 2Ω and 3Ω are combined in parallel and 1 Ω is in series to both )

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