physics MCQs - 12th class Chapter 02 Mcqs

1

The SI unit of electric current is the ampere, which is equivalent to a flow of charge at the rate of one coulomb per ______.

A

millisecond

B

second

C

minute

D

hour

2

In metallic conductors, the charge carriers are ______.

A

protons

B

ions

C

electrons

D

neutrons

3

The conventional current is defined as the direction of flow of ______ charges.

A

negative

B

positive

C

neutral

D

both positive and negative

4

The drift velocity of electrons in a conductor is typically of the order of ______.

A

10^3 m/s

B

10^6 m/s

C

10^-3 m/s

D

10^-6 m/s

5

A steady current is established in a wire when a constant ______ is maintained across it.

A

mass

B

pressure

C

temperature

D

potential difference

6

Which device converts chemical energy into electrical energy?

A

Solar cell

B

Electric generator

C

Thermocouple

D

Cell

7

The heating effect of current is given by the formula ______.

A

H = I*R*t

B

H = I^2*R*t

C

H = I*R^2*t

D

H = V*R*t

8

The study of chemical effects of current through certain liquids is known as ______.

A

electrolysis

B

hydrolysis

C

photolysis

D

thermolysis

9

In the electrolysis of copper sulphate solution, copper atoms are deposited at the ______.

A

anode

B

cathode

C

electrolyte

D

voltameter

10

Ohm's law states that the current flowing through a conductor is directly proportional to the ______ across its ends.

A

resistance

B

resistivity

C

potential difference

D

temperature

11

A conductor has a resistance of 1 ohm if a current of 1 ampere flows through it when a potential difference of ______ is applied.

A

1 volt

B

10 volts

C

0.1 volts

D

100 volts

12

Which of the following is an example of a non-ohmic device?

A

Copper wire

B

Silver wire

C

Filament bulb

D

Aluminum wire

13

The resistance of a wire is directly proportional to its ______.

A

area

B

volume

C

density

D

length

14

The SI unit of resistivity is ______.

A

ohm

B

mho

C

ohm-metre

D

siemen

15

Conductivity is the reciprocal of ______.

A

resistance

B

conductance

C

resistivity

D

current

16

Which of the following materials has the highest conductivity?

A

Iron

B

Gold

C

Copper

D

Tungsten

17

The temperature coefficient of resistance is defined as the fractional change in resistance per ______.

A

degree Celsius

B

ohm

C

kelvin

D

ampere

18

Substances like germanium and silicon have a ______ temperature coefficient of resistance.

A

positive

B

negative

C

zero

D

infinite

19

In the standard color code for carbon resistors, what digit does the color 'Red' represent?

A

0

B

1

C

2

D

3

20

A silver band on a carbon resistor indicates a tolerance of ______.

A

±5%

B

±10%

C

±20%

D

±1%

21

A rheostat can be used as a variable resistor and as a ______.

A

capacitor

B

inductor

C

potential divider

D

transistor

22

A thermistor is a ______ sensitive resistor.

A

light

B

pressure

C

heat

D

voltage

23

Most thermistors have a ______ temperature coefficient of resistance.

A

positive

B

negative

C

zero

D

constant

24

Electrical power can be calculated using the formula ______.

A

P = I/V

B

P = V/R

C

P = V*I

D

P = R/V

25

The unit of electromotive force (emf) is the ______.

A

newton

B

joule

C

ampere

D

volt

26

The internal resistance of a cell is due to the ______ present between its electrodes.

A

metal plates

B

electrolyte

C

external circuit

D

wire

27

When a current is drawn from a cell, its terminal potential difference is ______ its emf.

A

greater than

B

equal to

C

less than

D

twice

28

For maximum power to be delivered to a load, the load resistance must be ______ the internal resistance of the source.

A

greater than

B

less than

C

equal to

D

half of

29

Kirchhoff's first rule, ΣI = 0 at a junction, is a manifestation of the law of conservation of ______.

A

energy

B

momentum

C

charge

D

mass

30

Kirchhoff's second rule, which states that the algebraic sum of voltage changes in a loop is zero, is based on the law of conservation of ______.

A

charge

B

energy

C

mass

D

momentum

31

In a Wheatstone bridge, if the galvanometer shows no deflection, the ratio R1/R2 is equal to ______.

A

R3*R4

B

R3/R4

C

R4/R3

D

R3+R4

32

A potentiometer is an accurate instrument for measuring potential difference because it does not draw any ______ from the circuit.

A

voltage

B

power

C

resistance

D

current

33

In a metallic conductor, free electrons are in random motion with speeds that depend on ______.

A

pressure

B

temperature

C

volume

D

density

34

When an electric field is applied across a metallic conductor, the free electrons acquire an average velocity called ______.

A

random velocity

B

thermal velocity

C

drift velocity

D

escape velocity

35

The material in a voltameter which leads current into or out of the electrolyte is known as an ______.

A

electrode

B

anode

C

cathode

D

electrolyte

36

The electrode connected to the positive terminal of the current source is called the ______.

A

cathode

B

anode

C

diode

D

triode

37

The resistance of a conductor is a measure of the ______ to the motion of electrons.

A

assistance

B

pathway

C

opposition

D

attraction

38

The equivalent resistance of resistors connected in series is the ______ of their individual resistances.

A

sum

B

product

C

reciprocal of the sum

D

sum of the reciprocals

39

The equivalent resistance of resistors connected in parallel is found by the sum of the ______ of their individual resistances.

A

reciprocals

B

squares

C

products

D

sums

40

If a resistor has no fourth color band, its tolerance is understood to be ______.

A

±5%

B

±10%

C

±20%

D

±1%

41

A rheostat is typically made from a bare ______ wire wound over an insulating cylinder.

A

copper

B

aluminum

C

manganin

D

silver

42

Thermistors are very accurate for measuring low temperatures, especially near ______.

A

100 K

B

50 K

C

273 K

D

10 K

43

The power delivered to a resistor R by a current I is given by ______.

A

P = I*R

B

P = I*R^2

C

P = I^2*R

D

P = V/I

44

The emf of a source is the ______ supplied to a unit charge by the cell.

A

force

B

power

C

energy

D

resistance

45

When a circuit is open, a voltmeter connected across the terminals of a cell measures its ______.

A

current

B

internal resistance

C

terminal potential difference

D

emf

46

In a simple circuit, the terminal voltage of a battery is less than the emf by an amount ______.

A

IR

B

I/r

C

Ir

D

I/R

47

The condition for maximum power output from a source is ______.

A

R > r

B

R < r

C

R = r

D

R = 0

48

When traversing a resistor in the direction of current, the change in potential is considered ______ according to Kirchhoff's rules.

A

positive

B

negative

C

zero

D

infinite

49

A potentiometer works on the principle of a ______.

A

transformer

B

potential divider

C

full-wave rectifier

D

capacitor

50

To compare the emfs of two cells, E1 and E2, using a potentiometer, the ratio E1/E2 is equal to the ratio of their balancing ______.

A

resistances (r1/r2)

B

currents (I1/I2)

C

lengths (l1/l2)

D

powers (P1/P2)