Physics - Current Electricity - Quiz-1

If a resistance coil is made by joining in parallel two resistances each of 20 $Ω$ . An emf of 2V is applied across this coil for 100 seconds. The heat produced in the coil is

0%

20 J
0%

10 J
0%

40 J
0%

80 J

Which of the following graphs correctly represents the variation of mobility $(μ)$ of electrons with applied electric field (E) in a metallic conductor?

If I be the current limit of a fuse wire of length l and radius r, then select the appropriate relation

0%

$I α l$
0%

$I α r^{2}$
0%

$I α l^{0}$
0%

$I α r^{0}$

The resistance of platinum wire at 0 $° C$ is 22.05 $Ω$ and at 100 $° C$ it becomes 22.70 $Ω$ . When the wire is heated to a temperature of t $° C$ the resistance of wire becomes 24.91 $Ω$ . The value of t is

0%

220
0%

440
0%

310
0%

550

The sensitivity of a potentiometer can be increased by

0%

increasing the potential gradient
0%

decreasing the length of potentiometer wire
0%

decreasing the current in the potentiometer wire
0%

all of these

Masses of 3 wires of same metal are in the ratio 1 : 2 : 3 and their lengths are in the ratio 3 : 2 : 1. The electrical resistances are in ratio

0%

1 : 4 : 9
0%

9 : 4 : 1
0%

1 : 2 : 3
0%

27 : 6 : 1

A wire of radius r has resistance R. If it is stretched to a radius of $\frac{3 r}{4}$ , its resistance becomes

0%

$\frac{9 R}{16}$
0%

$\frac{16 R}{9}$
0%

$\frac{81 R}{256}$
0%

$\frac{256 R}{81}$

In the figure shown, the total resistance between A and B is

0%

12 Ω
0%

4 Ω
0%

6 Ω
0%

8 Ω

$In the circuit shown in figure if power dissipated in 9 Ω resistor is 144 W, then potential difference across 3.6 Ω resistor will be$

0%

36V
0%

18V
0%

9V
0%

Zero

A current of 1 mA is flowing through a copper wire. How many electrons will pass a given point in one second $[e = 1.6 \times 10^{- 19} Coulomb]$

0%

$6.25 \times 10^{19}$
0%

$6.25 \times 10^{15}$
0%

$6.25 \times 10^{31}$
0%

$6.25 \times 10^{8}$

The drift velocity of free electrons in a conductor is 'v' when a current 'i' is flowing in it. If both the radius and current are doubled, then drift velocity will be:

0%

v
0%

$\frac{v}{2}$
0%

$\frac{v}{4}$
0%

$\frac{v}{8}$

A battery has e.m.f. 4V and internal resistance r. When this battery is connected to an external resistance of 2 ohms, a current of 1 amp. flows in the circuit. How much current will flow if the terminals of the battery are connected directly?

0%

1 Amp
0%

2 Amp
0%

4 Amp
0%

Infinite

The current I as shown in the circuit will be:

0%

10 A
0%

$\frac{20}{3} A$
0%

$\frac{2}{3} A$
0%

$\frac{5}{3} A$

A meter bridge is set up to determine unknown resistance x using a standard 10 $Ω$ resistor. The galvanometer shows the null point when the tapping key is at a 52 cm mark. End corrections are 1 cm and 2 cm respectively for end A and B. Then the value of x is

0%

10.2 $Ω$
0%

10.6 $Ω$
0%

11.1 $Ω$
0%

10.8 $Ω$

The resistivity of iron is 1 × 10^–7 ohm – m. The resistance of iron wire of particular length and thickness is 1 ohm. If the length and the diameter of wire both are doubled, then the resistivity in ohm – m will be :

0%

1 × 10^–7
0%

2 × 10^–7
0%

4 × 10^–7
0%

8 × 10^–7

The resistivity of a wire :

0%

Increases with the length of the wire
0%

Decreases with the area of cross-section
0%

Decreases with the length and increases with the cross-section of the wire
0%

None of the above statement is correct

Drift velocity v_d varies with the intensity of electric field as per the relation

0%

$v_{d} \propto E$
0%

$v_{d} \propto \frac{1}{E}$
0%

v_d = constant
0%

$v_{d} \propto E^{2}$

In a conductor 4 coulombs of charge flows for 2 seconds. The value of electric current will be :

0%

4 volts
0%

4 amperes
0%

2 amperes
0%

2 volts

The specific resistance of a wire is ρ, its volume is 3 m³ and its resistance is 3 ohms, then its length will be

0%

$\sqrt{\frac{1}{ρ}}$
0%

$\frac{3}{\sqrt{ρ}}$
0%

$\frac{1}{ρ} \sqrt{3}$
0%

$ρ \sqrt{\frac{1}{3}}$

When a piece of aluminum wire of finite length is drawn through a series of dies to reduce its diameter to half its original value, its resistance will become :

0%

Two times
0%

Four times
0%

Eight times
0%

Sixteen times

Through a semiconductor, an electric current is due to drift off:

0%

Free electrons
0%

Free electrons and holes
0%

Positive and negative ions
0%

Protons

A metallic block has no potential difference applied across it, then the mean velocity of free electron is (T = absolute temperature of the block):

0%

proportional to T.
0%

proportional to $\sqrt{T.}$
0%

zero.
0%

finite but independent of temperature.

The specific resistance of all metals is most affected by :

0%

Temperature
0%

Pressure
0%

Degree of illumination
0%

Applied magnetic field

The positive temperature coefficient of resistance is for :

0%

Carbon
0%

Germanium
0%

Copper
0%

An electrolyte

The electric intensity E, current density j and specific resistance k are related to each other by the relation :

0%

E = jk
0%

E = k/j
0%

E = j/k
0%

k = jE

The resistance of a wire of uniform diameter d and length L is R. The resistance of another wire of the same material but diameter 2d and length 4L will be :

0%

2R
0%

R
0%

R/2
0%

R/4

There is a current of 1.344 amp in a copper wire whose area of cross-section normal to the length of the wire is 1 mm². If the number of free electrons per cm³ is 8.4 × 10²², then the drift velocity would be :

0%

(1) 0 mm/sec
0%

(2) 1.0 m/sec
0%

(3) 0.1 mm/sec
0%

(4) 0.01 mm/sec

An electric wire of length ‘I’ and area of cross-section a has a resistance R ohms. Another wire of the same material having the same length and area of cross-section 4a has a resistance of :

0%

4R
0%

R/4
0%

R/16
0%

16R

If n, e, τ and m respectively represent the density, charge relaxation time and mass of the electron, then the resistance of a wire of length l and area of cross-section A will be

0%

$\frac{m l}{n e^{2} τ A}$
0%

$\frac{m τ^{2} A}{n e^{2} l}$
0%

$\frac{n e^{2} τ A}{2 m l}$
0%

$\frac{n e^{2} A}{2 m τ l}$

The relaxation time in conductors :

0%

Increases with the increase in temperature
0%

Decreases with the increase in temperature
0%

It does not depend on the temperature
0%

All of the sudden changes at 400 K

0:0:1

Practice Physics Quiz Questions and Answers

0:0:1

Practice Physics Quiz Questions and Answers

Support mcqexams.com by disabling your adblocker.