How does the power dissipated in a resistor by an alternating current relate to the power dissipated by a direct current that has potential difference and current values that are equal to the maximum values of the alternating current?

A step-up transformer has exactly 50 turns in its primary and exactly 7000 turns in its secondary. If the applied emf in the primary is 120 V, what emf is induced in the secondary?

How can an ac generator be converted to a dc generator? Explain your answer.

A. What is the rms current in a light bulb that has a resistance of $25 \Omega$ and an rms emf of 120 V? What are the maximum values for current and emf?

Explain how Lenz's Jaw illustrates the principle of energy conservation.

According to alternating current theory, the currents and potential differences in the components of the circuit shown in the earlier figure are determined by Kirchhoff's laws and the relationships

$$I_1=\frac{V_1}{R_1}, \quad I_2=\frac{V_2}{R_2}, \quad I_3=i \omega C V_3, \quad V_4=i \omega L I_2 .$$

The factor $i=\sqrt{-1}$ in the expression for $I_3$ indicates that the phase of $I_3$ is $90^{\circ}$ ahead of $V_3$. Similarly the phase of $V_4$ is $90^{\circ}$ ahead of $I_2$.

Measurement shows that $V_3$ has an amplitude of $0.661 V_0$ and a phase of $+13.4^{\circ}$ relative to that of the power supply. Taking $V_0=1 \mathrm{~V}$, and using a series

A 256-turn coil with a cross-sectional area of 0.0025 $\mathrm{m}^{2}$ is placed in a uniform external magnetic field of strength 0.25 T so that the plane of the coil is perpendicular to the field. The coil is pulled steadily out of the field in 0.75 s. Find the average induced emf during this interval.

Which quantities remain constant when alternating currents are generated?

Explain what would happen if a commutator were not used in a motor.

The parts of the electromagnetic spectrum are commonly described in one of three ways. What are these ways?

A technician has two resistors, each of which has the same resistance, R. How many different resistances can the technician achieve?

The parts of the electromagnetic spectrum are commonly described in one of three ways. What are these ways?

What four factors affect the magnitude of the induced emf in a coil of wire?

You have two iron bars and a ball of string in your possession; one iron bar is magnetized, and one iron bar is not. How can you determine which iron bar is magnetized?