CBSE
Multiple Choice QuestionsAn inductor (L = 20 H), a resistor (R = 100 Ω) and a battery (E = 10 V) are connected in series. After a long time, the circuit is short-circuited and then the battery is disconnected. Find the current in the circuit at 1 ms after short circuiting.
4.5 x 105 A
3.2x 10-5 A
9.8 × 10-5 A
6.7 × 10-4 A
Assertion: At resonance, LCR series circuit have a minimum current.
Reason: At resonance, in LCR series circuit, the current and e.m.f are not in phase with each other.
If both assertion and reason are true and reason is the correct explanation of assertion.
If both assertion and reason are true but reason is not the correct explanation of assertion.
If assertion is true but reason is false.
If both assertion and reason are false.
The magnetic flux through each turn of a coil having 200 turns is given as (t2 1) x 10-3 Wb, where t is in second. The emf induced in the coil at t = 3s is
0.7 V
1.2 V
0.8 V
0.9 V
An inductive circuit contains a resistance of 10 Ω and an inductance of 2 H, If an AC voltage of 120 V and frequency 60 Hz is applied to this circuit, the current would be nearly
0.72 A
0.16 A
0.48 A
0.80 A
An L-C-R series circuit with a resistance of 100 Ω is connected to 200 V (AC source) and angular frequency 300 rad/s. When only the capacitor is removed, then the current lags behind the voltage by 60°. When only the inductor is removed the current leads the voltage by 60°. The average power dissipated in original L-C-R circuit is
50 W
100 W
200 W
400 W
In an oscillating system, a restoring force is a must. In an L-C circuit, restoring force is provide by
capacitor
inductance
resistance
both (a) and (b)
A circular coil of radius 10 cm, 500 turns and resistance 2 Ω is placed with its plane perpendicular to the horizontal component of the earth's magnetic field. It is rotated about its vertical diameter through 180° in 0.25 s. The
current induced in the coil is
(Horizontal component of the earth's magnetic field at that place is 3.0 x 10-5 T)
1.9 × 10-3 A
2.9 × 10-3 A
3.9 × 10-3 A
4.9 × 10-3 A
A beam of light travelling along X-axis is described by the electric field Ev = 600 . sin, the maximum magnetic force on a charge q = 2e, moving along Y-axis with the speed of 3 × 108 m/s is
19.2 × 10-17 N
1.92 × 10-17
0.192
None of these
A series resonant LCR circuit has a quality factor ( Q-factor) 0.4. If R = 2 kΩ, C = 0.1 μF, then the value of inductance is
0.1 H
0.064 H
2 H
5 H
In an LCR circuit as shown in figure, both switches are open initially. Now switch S1 is closed, S2 kept open. (q is charge on the capacitor and τ = RC is capacitive time constant). Which of the following statement is correct?
At t = , q = CV ( 1 e-1 )
Work done by the battery is half of the energy dissipated in the resistor
At t = τ, q = CV/2
At t = τ, q = CV ( 1 e-2 )
