Alternating Current Test

Result

Alternating Current Test - 4

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Question 1
1 / -0

____________ is the current that varies both in magnitude as well as direction periodically

A
Alternating Current

B
Direct Current

C
Eddy Current

D
None of the above

Solution

Alternating current is the current that varies both in magnitude as well as the direction alternatively. Hence the name alternating current.

Mathematically, it is represented as sinusoidal function of current.

I = I₀ sin ωt

Where I₀ is the peak current value of the alternating current in one cycle.
Question 2
1 / -0

The potential difference V and the current I flowing through an instrument in an ac circuit of frequency f are given by V = 5 cosωt V and I = 2 sinωt A (where ω = 2πf). The power dissipated in the instrument is,

A
Zero

B
10 W

C
5W

D
2.5 W

Solution

The power dissipated by a device in AC circuit is given by the expression,

P_rms = V_rms × I_rms × cosϕ, where ϕ is the phase angle between the voltage and the current.

Now, in the question it is given that,

V = 5 cos ωt = 5 sin (ωt + π/2) and the I = 2 sinωt.

The phase difference between the current and the voltage is 90°. Which is ϕ = π/2

Thus, power dissipated is given as,

Power = V_rms × I_rms × cosϕ = 5 sin (ωt + π/2) × I = 2 sinωt × cos (π /2) = 0
Question 3
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In a system containing two bodies A and B, the net charge equals _____

A
Charge on A

B
Charge on B

C
Charge on A + Charge on B

D
Zero

Solution

The net quantity of electric charge in a system is the algebraic sum of all charges present in it. The net charge in a system containing 2 charges A and B is charge on A + charge on B.