1. True or False? The induced EMF due to a changing magnetic flux creates a new

Question

1.True or False? The induced EMF due to a changing magnetic flux creates a new magnetic field that resists the changing magnetic flux.

2.True or False? Magnetic flux does depend on the strength of the magnetic field passing through some surface, but it does not depend on the angle that the field makes with that surface.

3.True or False? The magnitude of the EMF produced in a generator depends on the speed at which the generator turns.

4.

When I move a conductor through a magnetic field, the change in magnetic field creates a net change in magnetic flux. The EMF that is induced by this changing flux creates tiny motional currents that are called _______.

5.
True or False? In an RL circuit, the larger the value of R (i.e. the resistance of the circuit), the longer it takes the circuit to reach its final steady-state value (with all else being held constant).

6.

Suppose we measure the energy stored in some inductor to be E when there is a current I running through it. If I double the current in the inductor, the new total energy will become _____.

7.True or False? If I were to hook up an AC voltage source to a resistor, the voltage drop across the resistor would be in phase with the current in the circuit.

8.

I wish to use a step up transformer to turn an initial RMS AC voltage of 100 V into a final RMS AC voltage of 200 V. What is the ratio of the number of turns in the primary to the secondary?

Explanation / Answer

1)

True - That is called BACK EMF

2)

False. Since it depends on B and B depends on the direction and needs to have a perpendicular component, the angle is very important

3)

True, EMF = NBAw sin(wt)

w is speed, so faster speed, more voltage

4)

Eddy Currents (Choice 3)

5)

False - Since the time constant = L/R the time constant is ivnersely proportional to R. Increase R and decrease time.

6)

Since E = .5LI^2, you see that doubling the current quadruples the energy

Choice 6

7)

True, unless an inductor or capacitor were introduced. If its only a resistor then it is TRUE, but False if you added in other components.

8)

From N1/N2 = V1/V2, then 100/200 reduces to 1/2

Choice 2

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