# Practice set-1

Welcome to your Practice set-1

1.
An electron and proton are sent into an electric field. The ratio of force experienced by them is

1) 1 : 1
2) 1 : 1840
3) 1840 : 1
4) 1 : 9.11Deselect Answer

2.
Two point charges q and -2q are placed some distance d apart. If the electric field at the location of q is E, that at the location of -2q is

1) –E/2
2) –2E
3) E/2
4) – 4EDeselect Answer

3.
An electron is moving with constant velocity along x-axis. If a uniform electric field is applied along y-axis, then its path in the x-y plane will be

1) a straight line 2) a circle 3) a parabola 4) an ellipseDeselect Answer

4.
A hollow metal sphere of radius 5cm is charged such that the potential on its surface is 10V. The potential at the centre of the sphere is

1) 0 V
2) 10 V
3) same as at point 5cm away from the surface
4) same as at point 25cm from the surfaceDeselect Answer

5.
Two positive charges q and q are placed at the diagonally opposite corners of a square and two negative charges -q and -q are placed at the other two corners of the square. Then at the centre of the square the resultant electric intensity E and the net electric potential V are

1) E  ≠  0, V = 0
2) E = 0, V = 0
3) E = 0, V  ≠ 0
4) E  ≠ 0, V  ≠ 0Deselect Answer

6.
An electric dipole when placed in a uniform electric field will have minimum potential energy, if the angle between dipole moment and electric field is

1) zero
2) Π / 2
3) Π
4) 3Π / 2Deselect Answer

7.
Two condensers of unequal capacities are connected in series across a constant voltage d.c. source. The ratio of the potential differences across the condensers will be

1) direct proportion to their capacities
2) inverse proportion to their capacities
3) direct proportion to the square of their capacities
4) inverse proportion to the square root of their capacitiesDeselect Answer

8.
The resultant capacity between the points P and Q of the given figure is

1) 4 µF
2) 16/3 µF
3) 1.6 µF
4) 1 µFDeselect Answer

9.
The drift speed of an electron in a metal is of the order of

1) 10 ^–13 m/s
2) 10 ^–3 mm/s
3) 10 ^–4 m/s
4) 10 ^–30 m/sDeselect Answer

10.
When light falls on semiconductors, their resistance

1) decreases 2) increases 3) does not change 4) can’t be predictedDeselect Answer

11.
When a piece of aluminium wire of finite length is drawn through a series of dies to reduce its diameter to half its original value, its resistance will become

1) Two times 2) Four times 3) Eight times 4) Sixteen timesDeselect Answer

12.
Two bulbs are fitted in a room in the domestic electric installation. If one of them glows brighter than the other, then

1) the brighter bulb has smaller resistance
2) the brighter bulb has larger resistance
3) both the bulbs have the same resistance
4) nothing can be said about the resistance unless other factors are knownDeselect Answer

13.
In metre bridge experiment of resistances, the known and unknown resistances are interchanged . The error so removed is

1) end correction 2) index error 3) due to temperature effect 4) random errorDeselect Answer

14.
In metre bridge experiment of resistances, the known and unknown resistances are interchanged . The error so removed is

1) 1.5m
2) 1.25m
3) 10.05m

15.
In an experiment to determine the internal resistance of a cell with potentiometer, the balancing length is 165cm. When a resistance of 5 ohm is joined in parallel with the cell the balancing length is 150cm. The internal resistance of cell is

1) 2.2 Ω
2) 1.1 Ω
3) 3.3 Ω
4) 0.5 ΩDeselect Answer

16.
The current i drawn from the 5 volt source will be

1) 0.5 A
2) 2 A
3) 1.5 A

17.
Shown in the figure below is a meter-bridge set up with null deflection in the galvanometer. The value of the unknown resistor R

1) 13.75 Ω
2) 211 Ω
3) 110 Ω
4) 55 ΩDeselect Answer

18.
The geometric length of a bar magnet is 24 cm. The length of the magnet is

1) 24cm
2) 28.8cm
3) 20cm

19.
Two magnets have their lengths in the ratio 2:3 and their pole strengths in the ratio 3:4. The ratio of their magnetic moment is

1) 2 :1
2) 4 :1
3) 1 : 2
4) 1 : 4Deselect Answer

20.
The magnetic induction field strength at a distance 0.3 m on the axial line of a short bar magnet of moment 3.6 Am^2 is

1) 4.5 x 10 ^-4 T
2) 9 x 10 ^-4 T
3) 9 x 10 ^-5 T
4) 2.6 x 10 ^-5 TDeselect Answer

21.
If ‘N’ is the number of turns in a coil, the value of self inductance varies as

1) N^0
2) N
3) N^2

22.
In the circuit of figure, (1) and (2) are ammeters. Just after key K is pressed to complete the circuit, the reading is

1) maximum in both (1) and (2)
2) zero in both (1) and (2)
3) zero in (1), minimum in (2)
4) maximum in (1), zero in (2)Deselect Answer

23.
The average self-induced emf in a 25mH solenoid when the current in it falls from 0.2 A to 0 A in 0.01 second, is

1) 0.05 V
2) 0.5 V
3) 500 V
4) 50 VDeselect Answer

24.
In an AC circuit containing only capacitance the current

1) leads the voltage by 180º
2) lags the voltage by 90º
3) leads the voltage by 90º
4) remains in phase with the voltageDeselect Answer

25.
In an LCR a.c circuit at resonance, the current

1) Is always in phase with the voltage
2) Always leads the voltage
3) Always lags behind the voltage
4) May lead or lag behind the voltageDeselect Answer

26.
The peak voltage of 220 Volt AC mains (in Volt) is

1) 155.6
2) 220.0
3) 311

27.
A condenser of 10 µF and an inductor of 1H are connected in series with an A.C. source of frequency 50Hz. The impedance of the combination will be (take π^2 =10 )

1) zero
2) Infinity
3) 44.7 Ω
4) 5.67 ΩDeselect Answer

28.
In an A.C. circuit, the instantaneous values of e.m.f. and current are E = 200 sin 314t volt and I = sin(314t + π / 3) ampere then the average power consumed in watts is

1) 200
2) 100
3) 0

29.
The transformer ratio of a transformer is 10:1. The current in the primary circuit if the secondary current required is 100 A assuming the transformer be ideal, is

1) 500 A
2) 200 A
3) 1000 A

30.
The figure shows variation of R, XL and XC with frequency f in a series L, C, R circuit. Then for what frequency point, the circuit is inductive

1) A
2) B
3) C
4) All pointsDeselect Answer

31.
Assertion(A) : Force between two point charges at rest is not changed by the presence of third point charge between them. Reason(R): Force depends on the magnitude of the first two charges and seperation between them.

A. Both ‘A’ and ‘R’ are true and ‘R’ is the correct explanation of ‘A’
B. Both ‘A’ and ‘R’ are true and ‘R’ is not the correct explanation of ‘A’
C. ‘A’ is true and ‘R’ is false
D. ‘A’ is false and ‘R’ is trueDeselect Answer

32.
Assertion (A) : The net magnetic flux coming out of a closed surface is always zero. Reason (R) : Unlike poles of equal strength exist together.

A. Both ‘A’ and ‘R’ are true and ‘R’ is the correct explanation of ‘A’
B. Both ‘A’ and ‘R’ are true and ‘R’ is not the correct explanation of ‘A’
C. ‘A’ is true and ‘R’ is false
D. ‘A’ is false and ‘R’ is trueDeselect Answer

33.
Assertion (A): Two capacitors are connected in parallel to a battery. If a dielectric medium is inserted between the plates of one of the capacitors then the energy stored in the system will increase. Reason (R): On inserting dielectric medium between the plates of a capacitors, its capacity increases.

A. Both ‘A’ and ‘R’ are true and ‘R’ is the correct explanation of ‘A’
B. Both ‘A’ and ‘R’ are true and ‘R’ is not the correct explanation of ‘A’
C. ‘A’ is true and ‘R’ is false
D. ‘A’ is false and ‘R’ is trueDeselect Answer

34.
Assertion(A) : A metallic shield in the form of a hollow shell may be built to block an electric field. Reason(R) : In a hollow spherical conducting sphere , the electric field inside it is zero at every point.

A. Both ‘A’ and ‘R’ are true and ‘R’ is the correct explanation of ‘A’
B. Both ‘A’ and ‘R’ are true and ‘R’ is not the correct explanation of ‘A’
C. ‘A’ is true and ‘R’ is false
D. ‘A’ is false and ‘R’ is trueDeselect Answer

35.
Assertion (A) : The induced emf and current will be same in two identical loops of copper and aluminium, when rotated with same speed in the same magnetic field. Reason (R): Mutual induction does not depend on the orientation of the coils

A. Both ‘A’ and ‘R’ are true and ‘R’ is the correct explanation of ‘A’
B. Both ‘A’ and ‘R’ are true and ‘R’ is not the correct explanation of ‘A’
C. ‘A’ is true and ‘R’ is false
D. ‘A’ is false and ‘R’ is true
E. Both 'A' and "R' are falseDeselect Answer

36.
PASSAGE-1:

A 100Ω resistance is connected in series with a 4H inductor. The voltage across the resistor is, VR = (2.0V) sin (10^3 t).

Find the expression of circuit current

(A) (2 x 10^-2 A) sin (10^3 t)
(B) (2 x 10^-3 A) sin (10^3 t)
(C) (2 x 10^-2 A) sin (10^-3 t)
(D) (2 x 10^-3 A) sin (10^-3 t)

Find the inductive reactance

(A) 2 × 10^ 3 ohm (B) 3 × 10^ 3 ohm (C) 4 × 10^ 3 ohm (D) 5 × 10^ 3 ohm

Find amplitude of the voltage across the inductor.

(A) 40 V           (B) 60 V            (C) 80 V              (D) 90 VDeselect Answer

37.
PASSAGE-2:

Resistance value of an unknown resistor is calculated using the formula V = R I where V and I be the readings of the voltmeter and the ammeter respectively. Consider the circuits below. The internal resistances of the voltmeter and the ammeter (Rv and Rg respectively) are finite and non zero.

Let RA and RB be the calculated values in the two cases A and B respectively.

The relation between RA and the actual value R is

(A) R > RA
(B) R < RA
(C) R = RA
D) dependent upon E and r.

The relation between RB and the actual value R is

(A) R < RB
(B) R > RB
(C) R = RB
D) dependent upon E and r.

If the resistance of voltmeter is Rv = 1 kΩ and that of ammeter is Rg = 1Ω. the magnitude of the percentage error in the measurement of R (the value of R is nearly 10W) is

(A) zero in both cases
(B) non zero but equal in both cases
(C) more in circuit A
D) more in circuit B