Alternating Current Test

Result

Alternating Current Test - 35

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Question 1
4 / -1

A coil of 40 H inductance is connected in series with a resistance of 8 ohm and the combination is joined to the terminals of a 2V battery. The time constant of the circuit is

A
40s

B
20s

C
5s

D
1/5s

Solution
Question 2
4 / -1

One conducting U tube can slide inside another as shown in Fig maintaining electrical contacts between the tubes. The magnetic field B is perpendicular to the plane of the figure. If each tube moves towards the other at a constant speed V, then the e.m.f induced in the circuit in terms of B, l and V where l is the width of each tube, will be

A
2BlV

B
zero

C
-BlV

D
BlV

Solution
Question 3
4 / -1

The phase difference between the alternating current and emf is π/2. Which of the following cannot be the constituent of the circuit ?

A
L alone

B
L, C

C
R, L

D
C alone
Question 4
4 / -1

A circuit has a resistance of 12 ohm and an impedance of 15 ohm. The power factor of the circuit will be

A
0.125

B
1.25

C
0.4

D
0.8

Solution
Question 5
4 / -1

A coil of inductance 300 mH and resistance 2 Ω is connected to a source of voltage 2V. The current reaches half of its steady state value in

A
0.3s

B
0.15s

C
0.1 s

D
0.05s

Solution
Question 6
4 / -1

An infinitely long cylinder is kept parallel to a uniform magnetic field B directed along positive z-axis. The direction of induced current on the surface of cylinder as seen from the z axis will be

A
clockwise of the +ve z axis

B
anticlockwise of the +ve z axis

C
zero

D
along the magnetic field
Question 7
4 / -1

A magnet is made to oscillate with a particular frequency, passing through a coil as shown in Fig. The time variation of the magnitude of e.m.f. generated across the coil during one cycle is

A

B

C

D
Question 8
4 / -1

As shown in Fig a metal rod makes contact and completes the circuit. The circuit is perpendicular to the magnetic field with B = 0.15 T. If the resistance is 3Ω, force needed to move the rod with a constant speed of 2m/s is

A

B

C

D

Solution
Question 9
4 / -1

Three indentical coils, A, B and C are placed with their planes parallel to one another. Coils A and C carry currents as shown in Fig. Coils B and C are fixed in position and coil A is moved towards B. Then, current induced in B is in

A
clockwise current

B
anticlockwise current

C
no current is induced in B

D
current is induced only when both coils move
Question 10
4 / -1

A vertical ring of radius r and resistance R falls vertically. It is in contact with two vertical rails which are joined at the top. The rails are without friction and resistance. There is a horizontal uniform magnetic field of magnitude B perpendicular to the plane of the ring and the rails. When the speed of the ring is v, the current in the section PQ is

A
zero

B

C

D

Solution