(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

After you measure the self-inductance of a coil, you unwind it and then rewind half the length of wire into a coil with the same diameter but half the number of turns. How does this change the self-inductance?

a. It is the same.

b. It is doubled.

c. It is quadrupled.

d. It is halved.

e. It is quartered.

2. Relevant equations

See below.

3. The attempt at a solution

L = (N* magnetic flux)/i = (N*B*A*cos theta)/i = (n*l*A*B*cos theta)/(i), where N = n*l (l = wire length)

L2 = [(l/2)*A*(n/2)*B]/i = (1/4)*[(L*A*n*B)/i] = (1/4)*L??

1. The problem statement, all variables and given/known data

How much does the energy stored in an inductor change if the current through the inductor is doubled?

a. It remains the same.

b. It is doubled.

c. It is quadrupled.

d. It is halved.

e. It is quartered.

2. Relevant equations

See below.

3. The attempt at a solution

U = 0.5*L*I^2

U2 = 0.5*L*(2I)^2 = 4*0.5*L*I^2 = 4*U??

1. The problem statement, all variables and given/known data

The magnetic flux through a loop is made to vary according to the relation magnetic flux = 6t^2 + 7t + 1, where the units are SI. The emf induced in the loop when t = 2 s is

a. 38 V

b. 39 V

c. 40 V

d. 31 V

e. 19 V

2. Relevant equations

Emf_induced = -(d magnetic flux)/(dt)

3. The attempt at a solution

Taking the derivative, |emf| = 12t + 7, where t = 2 s

|Emf| = 12*(2s) + 7 = 31 V??

Thanks.

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# Homework Help: Inductance and Energy

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