Exam 19: Dc Circuits

A bar magnet is oriented above a copper ring, as shown in the figure. The magnet is dropped and passes completely through the ring. As viewed from above, what is the direction of the current induced in the ring after the magnet has completely passed through the ring and is somewhat below it?

The wire in the figure carries a current $I$ that is increasing with time at a constant rate. The wire and the three loops are all in the same plane. What is true about the currents induced in each of the three loops shown?

Three capacitors are arranged as shown in the figure, with a voltage source connected across the combination. $C _ { 1 }$ has a capacitance of $9.0 \mathrm { pF } , C _ { 2 }$ has a capacitance of $18.0 \mathrm { pF }$ , and $C _ { 3 }$ has a capacitance of $27.0 \mathrm { pF }$ . Find the potential drop across the entire arrangement if the potential drop across $C _ { 2 }$ is $257.0 \mathrm {~V}$ .

When an external resistor of resistance $R _ { 1 } = 14 \Omega$ is connected across the terminals of a battery, a current of $6.0 \mathrm {~A}$ flows through the resistor. When a different external resistor of resistance $R _ { 2 } = 64.4 \Omega$ is connected instead, the current is $2.0 \mathrm {~A}$ . Calculate (a) the emf of the battery and (b) the internal resistance of the battery.

A 22 -A current flows into a parallel combination of $4.0 - \Omega , 6.0 - \Omega$ , and $12 - \Omega$ resistors. What current flows through the $12 - \Omega$ resistor?

As shown in the figure, a uniform magnetic field $B$ is confined to a cylindrical volume of radius $0.050 \mathrm {~m}$ . This field is directed into the plane of the page and is increasing at a constant rate of $0.900 \mathrm {~T} / \mathrm { s }$ . Calculate the magnitude and direction (clockwise or counterclockwise) of the current induced in a circular wire ring of radius $0.16 \mathrm {~m}$ and resistance $7.1 \Omega$ that encircles the magnetic field region.

If $1.5$ A flows through $R _ { 2 }$ , what is the emf $V$ of the ideal battery in the figure?

Two capacitors are connected as shown in the figure, with $C _ { 1 } = 4.0 \mu \mathrm { F }$ and $C _ { 2 } = 7.0 \mu \mathrm { F }$ . If a voltage source $V = 90 \mathrm {~V}$ is applied across the combination, find the potential difference across $C _ { 1 }$ .

An series circuit consists of an ac voltage source, a resistor of resistance $810 \Omega$ , and an inductor. (There is no capacitance in the circuit.) The current amplitude is $0.40 \mathrm {~A}$ , and $\mathrm { t }$ phase angle between the source voltage and the current has magnitude $11 ^ { \circ }$ . (a) Does the source voltage lag or lead the current? (b) What is the voltage amplitude of the source? he

A $0.10 - \mu \mathrm { F }$ capacitor is connected to a $120 - \mathrm { V }$ rms $60 - \mathrm { Hz }$ source. (a) What is its capacitive reactance? (b) What is the rms current to the capacitor? (c) If both the capacitance and the frequency were doubled, what would be the rms current?

A 45- $\mathrm { mH }$ inductor is connected in series with a $60 - \Omega$ resistor through an ideal $15 - \mathrm { V }$ dc power supply and an open switch. What is the current $7.0 \mathrm {~ms}$ after closing the switch?

An ideal transformer has 60 turns on its primary coil and 300 turns on its secondary coil. If 120 V at 2.0 A is applied to the primary, what voltage and current are present in the secondary?

A $120 - \mathrm { V }$ rms voltage at $60 \mathrm {~Hz}$ is applied across an inductor and a $200 - \Omega$ resistor. If the impedance of this circuit is $216 \Omega$ , what is the rms value of the current?

What is the magnitude of the potential difference between points $\mathrm { A }$ and $\mathrm { C }$ for the circuit shown in the figure? The battery is ideal, and all the numbers are accurate to two significant figures.

You have available a galvanometer that gives a full-scale deflection for a $333 - \mu \mathrm { A }$ current and has a coil resistance of $33 \Omega$ . (a) What shunt resistance is needed to convert this galvanometer to a $5.0 - \mathrm { A }$ ammeter? (b) What series resistance is needed to convert this galvanometer to a $5.0 - \mathrm { V }$ voltmeter?

A $100 - \Omega$ resistor is connected in series with a $10.0 - \mathrm { mH }$ inductor across an ac source operating at $1.00 \mathrm { kHz }$ . What is the impedance of this circuit?

A circular wire ring is situated above a long straight wire, as shown in the figure. The straight wire has a current $I$ flowing to the right, and this current is increasing at a constant rate. Which of the following statements is true?

What is the reactance of a $20 - \mathrm { mH }$ inductor at a frequency of $60 \mathrm {~Hz}$ ?

A closed flat loop conductor with radius $2.0 \mathrm {~m}$ is located in a changing uniform magnetic field. If the emf induced in the loop is $2.0 \mathrm {~V}$ , what is the rate at which the magnetic field strength is changing if the magnetic field is oriented perpendicular to the plane in which the loop lies?

What is the reactance of a $1.0 - \mathrm { mH }$ inductor at $60 \mathrm {~Hz}$ ?