ALTERNATING CURRENT

The induced emf in a closed coil of wire, according to Faraday’s Law, is proportional to:

I. The magnitude of the magnetic flux

II. The magnetic flux density

III. The number of turns

IV. The rate of change of magnetic flux

• I

• II

• II and III (

• III and IV

• IV

A changing magnetic field B induces an emf Ɛ in a coil of radius R, as shown figure. What is the induced emf in the coil of radius 2R?

• Ɛ

• 2 Ɛ

• 4 Ɛ

• Ɛ/2

• Ɛ/4

A uniform magnetic field is distributed in the space of a circle of radius r, as shown in figure. The changing field induces an emf Ɛ in the loop with radius r. What is the induced emf in the loop with radius 2r?

• Ɛ

• 2 Ɛ

• 4 Ɛ

• Ɛ/2

• Ɛ/4

The number of turns in a long solenoid is doubled; how does the inductance of the solenoid change?

• It doesn’t change

• It doubles

• It quadruples

• It is cut to a half

• It is cut to a quarter

Which of the following is true about an inductor?

I. It stores energy

after the current stops flowing

II. It opposes the

change of current

III. It can produce a

magnetic field

• I

• III

• I and II

• II and III

• All of the above

Which of the following can act as an inductor?

I. A long coil

II. A long wire

III. A conducting sphere

• I

• III

• I and II

• II and III

• All of the above

At time t = 0, the switch is closed. Which of the following graphs best describes the voltage V across the resistance R as a function of time t?

• 
• 
• 
• 
• 

If L is inductance measured in H (Henry), what is 1 H equivalent to?

• 1 Vs/A

• 1 A/Vs

• 1 AV/s

• 1A∙s/V

• 1 s/A V

If R is 1 Ω and L is 1 H, then L/R is:

• 1 V

• 1 F

• 1 A

• 1 C

• 1 s

In the circuit given, what is the current at point P immediately after the switch is closed?

• Ɛ/R

• 2Ɛ/R

• Ɛ/2R

• LƐ/R

• 0