Exam 19: Dc Circuits

A $7.0 - \Omega$ resistor is connected across the terminals of a battery having an internal emf of $10 \mathrm {~V}$ . If $0.50 - \mathrm { A }$ current flows, what is the internal resistance of the battery?

What is the equivalent resistance in the circuit shown in the figure?

For the circuit shown in the figure, what is the power dissipated in the $2.0 - \Omega$ resistor? All the numbers shown are accurate to three significant figures.

An uncharged capacitor is connected in series with a resistor, a dc battery, and an open switch. At time t = 0 s, the switch is closed. Which of the graphs below best describes the Current I through the resistor as a function of time t?

You need an inductor that will store $20 \mathrm {~J}$ of energy when a $3.0$ -A current flows through it. What should be its self-inductance?

The potential applied to a $20 - \Omega$ resistor is $( 60 \mathrm {~V} ) \cos ( 33 t )$ . What is the average power consumed in the resistor?

What inductance must be put in series with a $100 - \mathrm { k } \Omega$ resistor at $1.0 - \mathrm { MHz }$ for a total impedance of $150 \mathrm { k } \Omega$ ?

The magnetic flux through a coil changes steadily from $4.0 \times 10 - 5 \mathrm {~T} \cdot \mathrm { m } ^ { 2 }$ to $5.0 \times 10 - 5 \mathrm {~T} \cdot \mathrm { m } ^ { 2 }$ in $0.10 \mathrm {~s}$ . What emf is induced in this coil?

What size capacitor should be placed in series with a $30 - \Omega$ resistor and a $40 - \mathrm { mH }$ inductive coil if the resonant frequency of the circuit is to be $1.0 \mathrm { kHz }$ ?

The phase angle of an $R L C$ series ac circuit with an inductive reactance of $200 \Omega$ and a capacitive reactance of $100 \Omega$ is $40.0 ^ { \circ }$ . What is the resistance of the resistor in this circuit?

A series circuit consists of an open switch, an ideal emf source $\varepsilon _ { 0 }$ , a $5.0 - \mathrm { k } \Omega$ resistor, and a 4.0-H inductor. If the potential across the resistor is $65.0 \mathrm {~V}$ at $2.0 \mathrm {~ms}$ after the switch is closed, find the source emf, $\varepsilon _ { 0 }$ .

A $200 - \Omega$ resistor, a 25-mH inductor, and a capacitor are connected in series across an ac voltage source at $1000 \mathrm {~Hz}$ . If the impedance of this circuit is $240 \Omega$ , which one of the following quantities could be the capacitance of the capacitor?

As shown in the figure, two parallel wires carry a current $I$ in opposite directions, and this current is decreasing. A rectangular loop is centered between the wires. The direction of the induced current through the resistor $R$ is

Three resistors with resistances of $2.0 \Omega , 6.0 \Omega$ , and $12 \Omega$ are connected across an ideal dc voltage source $V = 2.0 \mathrm {~V}$ , as shown in the figure. What is the total current $I$ in this circuit?

A flat circular loop having one turn and radius 5.0 cm is positioned with its plane perpendicular to a uniform 0.60-T magnetic field. The area of the loop is suddenly reduced to essentially zero in 0.50 ms. What emf is induced in the loop?

At what frequency will a $20.0 - \mathrm { mH }$ inductor have an inductive reactance of $100 \Omega$ ?

A $6.0 - \Omega$ and a $12 - \Omega$ resistor are connected in parallel across an ideal $36 - \mathrm { V }$ battery. What power is dissipated by the $6.0 - \Omega$ resistor?

At what frequency is the reactance of a $20.0 - \mathrm { mH }$ inductor equal to $120 \Omega$ ?

A 8.0- $\mu \mathrm { F }$ uncharged capacitor is connected in series with a 6.0- $\mathrm { k } \Omega$ resistor, an ideal $20 - \mathrm { V } \mathrm { dc }$ source, and an open switch. If the switch is closed at time $t = 0.0 \mathrm {~s}$ , what is the charge on the capacitor at $t = 9.0 \mathrm {~ms}$ ?

A $5 - \mu \mathrm { F }$ , a $7 - \mu \mathrm { F }$ , and an unknown capacitor $C \mathrm { X }$ are connected in series between points $a$ and $b$ . What do you know about the equivalent capacitance $C _ { a b }$ between $a$ and $b$ ? (There could be more than one correct choice.)