Alternating Current Test

Result

Alternating Current Test - 63

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Weekly Quiz Competition

Question 1
1 / -0

In the circuit shown how soon will the coil current reach $$\eta$$ fraction of the steady - state value

A
$$\frac { L } { R }$$

B
$$\frac { L } { R } \ln \frac { \eta } { ( 1 - \eta ) }$$

C
$$\frac { L } { R } \ln \frac { 1 } { ( 1 - \eta ) }$$

D
$$\frac { L } { R } \ln ( 1 - \eta )$$
Question 2
1 / -0

The reactance of a coil when used in the domestic AC power supply (220 V 50 cycles) is 100 Ohm. The self inductance of the coil is nearly

A
3.2 Henry

B
0.32 Henry

C
2.2 Henry

D
0.22 Henry

Solution

AS we know,
Reactance $$ = 2 \pi \nu L \, \Rightarrow \, 100 \Omega = 2 \times \dfrac{22}{7} \times 50 \times L $$
$$ \therefore \, L = 0.32 $$ henry
Question 3
1 / -0

The correct phase diagram representing the relation between I$$_L$$ , I$$_C$$ and E in an anti-resonant LC circuit is:

A

B

C

D
None of these.
Question 4
1 / -0

An ideal inductor takes a current of 10 A when connected to a $$ 125 {V}, 50 {Hz} $$ ac supply.A pure resistor across the same source takes 12.5 A.If the two are connected in series across a $$ 100 {V}, 40 {Hz} $$ -supply,the current through the circuit will be

A
7 A

B
12.5 A

C
20 A

D
25 A
Question 5
1 / -0

Equivalent inductance of the circuit shown in the figure is

A
$$1.0 H$$

B
$$1.75 H$$

C
$$0.75 H$$

D
$$0.25 H$$

Solution
Question 6
1 / -0

Impedance of LR circuit is-

A
$$R^2+\omega ^2L^2$$

B
$$\sqrt {R+\omega L}$$

C
$$R+\omega L$$

D
$$\sqrt {R^2+\omega ^2 L^2}$$

Solution
Question 7
1 / -0

In an electric circuit applied ac emf is $$e = 20 \sin 300 \ t$$ volt and the current is $$i = 4 \sin 300 \ t$$ ampere.The reactance of the circuit is

A
$$5 \Omega$$

B
$$80 \Omega$$

C
$$1.8 \mathrm { k } \Omega$$

D
$$0$$

Solution
Question 8
1 / -0

Impedance of a coil having inductance $$0.4H$$ at frequency of $$50Hz$$ will be

A
$$20\pi \Omega$$

B
$$40\pi \Omega$$

C
$$2\pi \Omega$$

D
$$4\pi \Omega$$

Solution
Question 9
1 / -0

Above the resonant frequency,

A
the frequency of the body is less than the frequency of the external periodic force.

B
the frequency of the body is greater than the frequency of the external periodic force.

C
the frequency of the body is exactly equal to the frequency of the external periodic force.

D
both (A) and (B)

Solution

The maximum energy transfer from one osccillatory system to other when their frequency are equal and this frequency is called resonat frequency.
Ans. (C)
Question 10
1 / -0

The resonance frequency changes if .is a change in L-C-R series A.C. circuit.

A
only R

B
only L

C
only C

D
L and C