NCERT Exemplar Physics - Class 12>Chapter 7 - Alternating Current>SA>Q 7.21

EASY

12th CBSE

IMPORTANT

Earn 100

A device $‘ X ’$ is connected to an a.c source. The variation of voltage, current and power in one complete cycle is shown in Fig 7.5.

(b) What is the average power consumption over a cycle?

Important Questions on Alternating Current

EASY

12th CBSE

IMPORTANT

NCERT Exemplar Physics - Class 12>Chapter 7 - Alternating Current>SA>Q 7.21

A device $‘ X ’$ is connected to an a.c source. The variation of voltage, current and power in one complete cycle is shown in Fig 7.5.

(c) Identify the device $‘ X ’$ .

Question Image

EASY

12th CBSE

IMPORTANT

NCERT Exemplar Physics - Class 12>Chapter 7 - Alternating Current>SA>Q 7.22

Both alternating current and direct current are measured in amperes. But how is the ampere defined for an alternating current?

EASY

12th CBSE

IMPORTANT

NCERT Exemplar Physics - Class 12>Chapter 7 - Alternating Current>SA>Q 7.23

A coil of

0.01

henry inductance and

1

ohm resistance is connected to

200

volt,

50 H z

ac supply. Find the impedance of the circuit and time lag between max. alternating voltage and current.

MEDIUM

12th CBSE

IMPORTANT

NCERT Exemplar Physics - Class 12>Chapter 7 - Alternating Current>SA>Q 7.24

A

60 W

load is connected to the secondary of a transformer whose primary draws line voltage. If a current of

0.54 A

flows in the load, what is the current in the primary coil? Comment on the type of transformer being used.

MEDIUM

12th CBSE

IMPORTANT

NCERT Exemplar Physics - Class 12>Chapter 7 - Alternating Current>SA>Q 7.25

Explain why the reactance provided by a capacitor to an alternating current decreases with increasing frequency.

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12th CBSE

IMPORTANT

NCERT Exemplar Physics - Class 12>Chapter 7 - Alternating Current>SA>Q 7.26

Explain why the reactance offered by an inductor increases with the increasing frequency of an alternating voltage.

HARD

12th CBSE

IMPORTANT

NCERT Exemplar Physics - Class 12>Chapter 7 - Alternating Current>LA>Q 7.27

An electrical device draws

2 kW, 50 kV

power from AC mains voltage

223 V (r m s)

. The current differs (lags) in phase by

ϕ (\tan ϕ = \frac{- 3}{4})

as compared to voltage. Find (i)

R

, (ii)

X_{C} - X_{L}

, and (iii)

I_{M}

. Another device has twice the values for

R, X_{C}

and

X_{L}

. How are the answers affected?

MEDIUM

12th CBSE

IMPORTANT

NCERT Exemplar Physics - Class 12>Chapter 7 - Alternating Current>LA>Q 7.28

1 MW

power is to be delivered from a power station to a town

10 km

away. One uses a pair of

Cu

wires of radius

0.5 c m

for this purpose. Calculate the fraction of ohmic losses to the power transmitted if
(i) power is transmitted at

220 V

. Comment on the feasibility of doing this.