Question 1

The total energy in an LC circuit is 5.0 *10-6 J. If L = 25 mH the maximum current is:

Accepted Answer

A)  10 mA 
B)  14 mA 
C)  20 mA 
D)  28 mA 
E)  40 mA 
A)  10 mA 
B)  14 mA 
C)  20 mA 
D)  28 mA 
E)  40 mA

Question 2

An RL series circuit is connected to an ac generator with a maximum emf of 20 V. If the maximum potential difference across the resistor is 16 V, then the maximum potential difference across the inductor is:

Accepted Answer

A)  2 V 
B)  4 V 
C)  12 V 
D)  25.6 V 
E)  36 V 
A)  2 V 
B)  4 V 
C)  12 V 
D)  25.6 V 
E)  36 V

Question 3

An LC circuit has a capacitance of 30 $\mu$F and an inductance of 15 mH. At time t = 0 the charge on the capacitor is 10 $\mu$C and the current is 20 mA. The maximum current is:

Accepted Answer

A)  18 mA 
B)  20 mA 
C)  25 mA 
D)  35 mA 
E)  42 mA 
A)  18 mA 
B)  20 mA 
C)  25 mA 
D)  35 mA 
E)  42 mA

Question 4

A 150-g block on the end of a spring with a spring constant of 35 N/m is pulled aside 25 cm and released from rest. In the electrical analog the initial charge on the capacitor is:

Accepted Answer

A)  0.15 C 
B)  6.67 C 
C)  0.025 C 
D)  40 C 
E)  35 C 
A)  0.15 C 
B)  6.67 C 
C)  0.025 C 
D)  40 C 
E)  35 C

Question 5

An ac generator producing 10 V (rms) at 200 rad/s is connected in series with a 50-$\Omega$ resistor, a 400-mH inductor, and a 200-$\mu$F capacitor. The rms current in amperes is:

Accepted Answer

A)  0.125 
B)  0.135 
C)  0.18 
D)  0.20 
E)  0.40 
A)  0.125 
B)  0.135 
C)  0.18 
D)  0.20 
E)  0.40

Question 6

A charged capacitor and an inductor are connected in series. At time t = 0 the current is zero, but the capacitor is charged. If T is the period of the resulting oscillations, the next time, after t = 0 that the energy stored in the magnetic field of the inductor is a maximum is:

Accepted Answer

A)  T 
B)  T/4 
C)  T/2 
D)  T/1 
E)  2T 
A)  T 
B)  T/4 
C)  T/2 
D)  T/1 
E)  2T

Question 7

The ideal meters shown read rms current and voltage. The average power delivered to the load is:

Accepted Answer

A)  definitely equal to VI 
B)  perhaps more than VI 
C)  possibly equal to VI even if the load contains an inductor and a capacitor 
D)  definitely less than VI 
E)  zero as is the average of any sine wave 
A)  definitely equal to VI 
B)  perhaps more than VI 
C)  possibly equal to VI even if the load contains an inductor and a capacitor 
D)  definitely less than VI 
E)  zero as is the average of any sine wave

Question 8

A step-down transformer is used to:

Accepted Answer

A)  increase the power 
B)  decrease the power 
C)  increase the voltage 
D)  decrease the voltage 
E)  change ac to dc 
A)  increase the power 
B)  decrease the power 
C)  increase the voltage 
D)  decrease the voltage 
E)  change ac to dc

Question 9

The average power supplied to the circuit shown passes through a maximum when which one of the following is increased continuously from a very low to a very high value?

Accepted Answer

A)  source emf   
B)  R 
C)  C 
D)  source frequency f 
E)  none of these 
A)  source emf   
B)  R 
C)  C 
D)  source frequency f 
E)  none of these

Question 10

An ac generator producing 10 V (rms) at 200 rad/s is connected in series with a 50-$\Omega$ resistor, a 400-mH inductor, and a 200-$\mu$F capacitor. The rms voltage (in volts) across the resistor is:

Accepted Answer

A)  2.5 
B)  3.4 
C)  6.7 
D)  10.0 
E)  10.8 
A)  2.5 
B)  3.4 
C)  6.7 
D)  10.0 
E)  10.8

Question 11

The core of a transformer is made in a laminated form to:

Accepted Answer

A)  facilitate easy assembly 
B)  reduce i2R losses in the coils 
C)  increase the magnetic flux 
D)  save weight 
E)  prevent eddy currents 
A)  facilitate easy assembly 
B)  reduce i2R losses in the coils 
C)  increase the magnetic flux 
D)  save weight 
E)  prevent eddy currents

Question 12

An electric motor, under load, has an effective resistance of 30  $\Omega$  and an inductive reactance of 40  $\Omega$ . When powered by a source with a maximum voltage of 420 V, the maximum current is:

Accepted Answer

A)  6.0 A 
B)  8.4 A 
C)  10.5 A 
D)  12.0 A 
E)  14.0 A 
A)  6.0 A 
B)  8.4 A 
C)  10.5 A 
D)  12.0 A 
E)  14.0 A

Question 13

In an RLC series circuit, which is connected to a source of emf $\varepsilon$mcos($ \omega $t), the current lags the voltage by 45 $\degree$ if:

Accepted Answer

A)  R = 1/$ \omega $C - $ \omega $L 
B)  R = 1/$ \omega $L - $ \omega $C 
C)  R = $ \omega $L - 1/$ \omega $C 
D)  R = $ \omega $C - 1/$ \omega $L 
E)  $ \omega $L = 1/$ \omega $C 
A)  R = 1/$ \omega $C - $ \omega $L 
B)  R = 1/$ \omega $L - $ \omega $C 
C)  R = $ \omega $L - 1/$ \omega $C 
D)  R = $ \omega $C - 1/$ \omega $L 
E)  $ \omega $L = 1/$ \omega $C

Question 14

A charged capacitor and an inductor are connected in series. At time t = 0 the current is zero, but the capacitor is charged. If T is the period of the resulting oscillations, the next time, after t = 0 that the charge on the capacitor is a maximum is:

Accepted Answer

A)  T/1 
B)  T/4 
C)  T/2 
D)  T 
E)  2T 
A)  T/1 
B)  T/4 
C)  T/2 
D)  T 
E)  2T

Question 15

The total energy in an LC circuit is 5.0 *10-6 J. If C = 15 $\mu$F the charge on the capacitor is:

Accepted Answer

A)  0.82 $\mu$C 
B)  8.5 $\mu$C 
C)  12 $\mu$C 
D)  17 $\mu$C 
E)  24 $\mu$C 
A)  0.82 $\mu$C 
B)  8.5 $\mu$C 
C)  12 $\mu$C 
D)  17 $\mu$C 
E)  24 $\mu$C

Question 16

An LC series circuit with an inductance L and a capacitance C has an oscillation frequency f. Two inductors, each with inductance L, and two capacitors, each with capacitance C, are all wired in series and the circuit is completed. The oscillation frequency is:

Accepted Answer

A)  f/4 
B)  f/2 
C)  f 
D)  2f 
E)  4f 
A)  f/4 
B)  f/2 
C)  f 
D)  2f 
E)  4f

Question 17

At time t = 0 the charge on the 50-$\mu$F capacitor in an LC circuit is 15 $\mu$C and there is no current. If the inductance is 20 mH the maximum current is:

Accepted Answer

A)  15 nA 
B)  15 $\mu$A 
C)  6.7 mA 
D)  15 mA 
E)  15 A 
A)  15 nA 
B)  15 $\mu$A 
C)  6.7 mA 
D)  15 mA 
E)  15 A

Question 18

The rapid exponential decay in just a few cycles of the charge on the plates of capacitor in an RLC circuit might due to:

Accepted Answer

A)  a large inductance 
B)  a large capacitance 
C)  a small capacitance 
D)  a large resistance 
E)  a small resistance 
A)  a large inductance 
B)  a large capacitance 
C)  a small capacitance 
D)  a large resistance 
E)  a small resistance

Question 19

An LC circuit has an inductance of 20 mH and a capacitance of 5.0 $\mu$F. At time t = 0 the charge on the capacitor is 3.0 F$\mu$C and the current is 7.0 mA. The total energy is:

Accepted Answer

A)  4.1 *10-7 J 
B)  4.9 * 10-7 J 
C)  9.0* 10-7 J 
D)  1.4 *10-6 J 
E)  2.8 * 10-6 J 
A)  4.1 *10-7 J 
B)  4.9 * 10-7 J 
C)  9.0* 10-7 J 
D)  1.4 *10-6 J 
E)  2.8 * 10-6 J

Question 20

The rms value of a sinusoidal voltage is   , where V0 is the amplitude. What is the rms value of its fully rectified wave? Recall that Vrect(t) = $\mid$V(t)$\mid$.

Accepted Answer

A)    
B)    
C)    
D)    
E)    
A)    
B)    
C)    
D)    
E)

Exam 31: Electromagnetic Oscillations and Alternating Current

The total energy in an LC circuit is 5.0 *10-6 J. If L = 25 mH the maximum current is:

An RL series circuit is connected to an ac generator with a maximum emf of 20 V. If the maximum potential difference across the resistor is 16 V, then the maximum potential difference across the inductor is:

An LC circuit has a capacitance of 30 μ\muμ F and an inductance of 15 mH. At time t = 0 the charge on the capacitor is 10 μ\muμ C and the current is 20 mA. The maximum current is:

A 150-g block on the end of a spring with a spring constant of 35 N/m is pulled aside 25 cm and released from rest. In the electrical analog the initial charge on the capacitor is:

An ac generator producing 10 V (rms) at 200 rad/s is connected in series with a 50- Ω\OmegaΩ resistor, a 400-mH inductor, and a 200- μ\muμ F capacitor. The rms current in amperes is:

A charged capacitor and an inductor are connected in series. At time t = 0 the current is zero, but the capacitor is charged. If T is the period of the resulting oscillations, the next time, after t = 0 that the energy stored in the magnetic field of the inductor is a maximum is:

The ideal meters shown read rms current and voltage. The average power delivered to the load is:

A step-down transformer is used to:

The average power supplied to the circuit shown passes through a maximum when which one of the following is increased continuously from a very low to a very high value?

An ac generator producing 10 V (rms) at 200 rad/s is connected in series with a 50- Ω\OmegaΩ resistor, a 400-mH inductor, and a 200- μ\muμ F capacitor. The rms voltage (in volts) across the resistor is:

The core of a transformer is made in a laminated form to:

An electric motor, under load, has an effective resistance of 30 Ω\OmegaΩ and an inductive reactance of 40 Ω\OmegaΩ . When powered by a source with a maximum voltage of 420 V, the maximum current is:

In an RLC series circuit, which is connected to a source of emf ε\varepsilonε mcos( ω \omega ω t), the current lags the voltage by 45 °\degree° if:

A charged capacitor and an inductor are connected in series. At time t = 0 the current is zero, but the capacitor is charged. If T is the period of the resulting oscillations, the next time, after t = 0 that the charge on the capacitor is a maximum is:

The total energy in an LC circuit is 5.0 *10-6 J. If C = 15 μ\muμ F the charge on the capacitor is:

An LC series circuit with an inductance L and a capacitance C has an oscillation frequency f. Two inductors, each with inductance L, and two capacitors, each with capacitance C, are all wired in series and the circuit is completed. The oscillation frequency is:

At time t = 0 the charge on the 50- μ\muμ F capacitor in an LC circuit is 15 μ\muμ C and there is no current. If the inductance is 20 mH the maximum current is:

The rapid exponential decay in just a few cycles of the charge on the plates of capacitor in an RLC circuit might due to:

An LC circuit has an inductance of 20 mH and a capacitance of 5.0 μ\muμ F. At time t = 0 the charge on the capacitor is 3.0 F μ\muμ C and the current is 7.0 mA. The total energy is:

The rms value of a sinusoidal voltage is , where V0 is the amplitude. What is the rms value of its fully rectified wave? Recall that Vrect(t) = ∣\mid∣ V(t) ∣\mid∣ .

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Filters

The total energy in an LC circuit is 5.0 *10^-⁶ J. If L = 25 mH the maximum current is:

An LC circuit has a capacitance of 30 $\mu$ F and an inductance of 15 mH. At time t = 0 the charge on the capacitor is 10 $\mu$ C and the current is 20 mA. The maximum current is:

An ac generator producing 10 V (rms) at 200 rad/s is connected in series with a 50- $\Omega$ resistor, a 400-mH inductor, and a 200- $\mu$ F capacitor. The rms current in amperes is:

An ac generator producing 10 V (rms) at 200 rad/s is connected in series with a 50- $\Omega$ resistor, a 400-mH inductor, and a 200- $\mu$ F capacitor. The rms voltage (in volts) across the resistor is:

An electric motor, under load, has an effective resistance of 30 $\Omega$ and an inductive reactance of 40 $\Omega$ . When powered by a source with a maximum voltage of 420 V, the maximum current is:

In an RLC series circuit, which is connected to a source of emf $\varepsilon$ _mcos( $\omega$ t), the current lags the voltage by 45 $\degree$ if:

The total energy in an LC circuit is 5.0 *10^-⁶ J. If C = 15 $\mu$ F the charge on the capacitor is:

At time t = 0 the charge on the 50- $\mu$ F capacitor in an LC circuit is 15 $\mu$ C and there is no current. If the inductance is 20 mH the maximum current is:

An LC circuit has an inductance of 20 mH and a capacitance of 5.0 $\mu$ F. At time t = 0 the charge on the capacitor is 3.0 F $\mu$ C and the current is 7.0 mA. The total energy is: