Describe the ways in which Eddy currents are used to advantage.

When bulk pieces of conductors are subjected to changing magnetic flux, induced currents produced in them are called eddy currents. The eddy currents can be used to advantage in the following ways: (i) Magnetic braking in trains: Strong electromagnets are situated above the rails in electrically powered trains. When electromagnets are activated, the eddy currents induced in the rails oppose the motion of the train. As there are no mechanical linkages, the braking effect is smooth. (ii) Electromagnetic damping: Moving coil galvanometers have a fixed core made of nonmagnetic metallic material. When the coil oscillates, the eddy currents generated in the core oppose the motion and bring the coil to rest quickly. (iii) Induction furnace: It can be used to produce high temperatures and can be utilised to prepare alloys by melting the constituent metals. A high frequency alternating current is passed through a coil which surrounds the metal to be melted. The eddy currents generated in the metals produce high temperatures sufficient to melt. (iv) Electric power meters: A metal disc is present inside it. Electric currents are induced in it, and it rotates in a magnetic field induced by the alternating current in the coil.

EASY

12th Tamil Nadu Board

IMPORTANT

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An alternating voltage of $260 V$ and $ω = 100 rad s^{- 1}$ is applied across an $L C R$ series circuit, where $L = 0.01 H, C = 4 \times 10^{- 4} F$ and $R = 10 Ω$ . The power supplied by the source is:

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Important Questions on Electromagnetic Induction and Alternating Current

EASY

12th Tamil Nadu Board

IMPORTANT

Physics Crash Course (Based on Revised Syllabus-2023)>Chapter 4 - Electromagnetic Induction and Alternating Current>Exercise>Q 152

The instantaneous power in an inductive a.c. circuit is

EASY

12th Tamil Nadu Board

IMPORTANT

Physics Crash Course (Based on Revised Syllabus-2023)>Chapter 4 - Electromagnetic Induction and Alternating Current>Exercise>Q 153

In an

AC

circuit, power is consumed in :

MEDIUM

12th Tamil Nadu Board

IMPORTANT

Physics Crash Course (Based on Revised Syllabus-2023)>Chapter 4 - Electromagnetic Induction and Alternating Current>Exercise>Q 154

What will be

RMS

value of wattless current?

MEDIUM

12th Tamil Nadu Board

IMPORTANT

Physics Crash Course (Based on Revised Syllabus-2023)>Chapter 4 - Electromagnetic Induction and Alternating Current>Exercise>Q 155

An ammeter shows that an alternator is delivering

20 A

. The voltmeter reads

220 V,

while a watt meter shows that

4 kW

of power is being delivered. Find the power factor.

HARD

12th Tamil Nadu Board

IMPORTANT

Physics Crash Course (Based on Revised Syllabus-2023)>Chapter 4 - Electromagnetic Induction and Alternating Current>Exercise>Q 156

A LCR circuit with resistors, capacitors and inductors connected in series have the following values

R = 20 Ω, L = 1.5 H and C = 35 μF

. This combination of LCR series circuit has been connected to a variable frequency and a supply voltage of

200 V

ac supply. Calculate the average power that is transferred to the above connection in the entire cycle, when the supply frequency and the natural frequency are equal.

MEDIUM

12th Tamil Nadu Board

IMPORTANT

Physics Crash Course (Based on Revised Syllabus-2023)>Chapter 4 - Electromagnetic Induction and Alternating Current>Exercise>Q 157

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.

MEDIUM

12th Tamil Nadu Board

IMPORTANT

Physics Crash Course (Based on Revised Syllabus-2023)>Chapter 4 - Electromagnetic Induction and Alternating Current>Exercise>Q 158

What will be value of power factor in AC circuit for inductor, capacitor and resistor?

HARD

12th Tamil Nadu Board

IMPORTANT

Physics Crash Course (Based on Revised Syllabus-2023)>Chapter 4 - Electromagnetic Induction and Alternating Current>Exercise>Q 159

A circuit containing a

80 m H

inductor and a

60 µ F

capacitor in series is connected to a

230 V

50 H z

supply. Suppose the circuit has a resistance of

15 Ω

. Obtain the average power transferred to each element of the circuit, and the total power absorbed.

An alternating voltage of 260 V and ω=100 rad s-1 is applied across an LCR series circuit, where L=0.01 H, C=4×10-4 F and R=10 Ω. The power supplied by the source is:

Important Questions on Electromagnetic Induction and Alternating Current

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An alternating voltage of $260 V$ and $ω = 100 rad s^{- 1}$ is applied across an $L C R$ series circuit, where $L = 0.01 H, C = 4 \times 10^{- 4} F$ and $R = 10 Ω$ . The power supplied by the source is: