CHAPTER 1

ELECTRICITY, MAGNETISM, AND ELECTRIC CIRCUITS

What is the flux density of a magnetic field whose flux is 3000 µWb and cross-sectional area is 0.25 m²?

A. 12,000 µT

B. 83,330 T

C. 0 T

D. More information is needed in order to find flux density.

A

The resonant circuit of a tuned-collector transistor oscillator has a resonant frequency of 5 MHz. If the value of capacitance is increased by 50%, calculate the new resonant frequency.

A. 3.33 MHz

B. 2.6 MHz

C. 11.25 MHz

D. 4.08 MHz

D

A highpass filter has R = 470 Ω and C = 2.2 µF. What is the impedance of the capacitor at 10 kHz?

A. 3.27 Ω

B. 2.37 Ω

C. 7.32 Ω

D. 7.23 Ω

D

A flux density of 1.2 T is produced in a piece of cast steel by a magnetizing force of 1250 A/m. Find the relative permeability of the steel under these conditions.

A. 674

B. 764

C. 476

D. 746

B

Given that v = 140 sin(4000t − 10°) in the circuit shown below, determine the voltage across the capacitor C1.

Circuit description:

Series RLC circuit with:

R1 = 3.6 kΩ

L1 = 1.2 H

C1 = 40 nF

Source voltage v = 140 sin(4000t − 10°)

A. 225.45 sin(4000t − 78.1°) V

B. 252.45 sin(4000t − 87.1°) V

C. 252.45 sin(4000t − 78.1°) V

D. 225.45 sin(4000t − 87.1°) V

A

Determine the power factor of a circuit that absorbs 1.5 kW for a 120-V input voltage and a 16-A current.

A. 0.871

B. 0.781

C. 0.178

D. 0.187

B

When connected to a 120-V rms, 60-Hz power line, a load absorbs 4 kW at a lagging power factor of 0.8. Find the value of capacitance necessary to raise the power factor to 0.95.

A. 103 µF

B. 310 µF

C. 340 µF

D. 403 µF

B

Suppose a voltage source has an internal resistance of 50 Ω. Which of the following load resistances will make the voltage source stiff?

A. 100 Ω

B. 500 Ω

C. 5000 Ω

D. 250 Ω

C

What is the total power loss if 2 kΩ and 1 kΩ parallel-connected resistors have a total current of 3 mA?

A. 6 µW

B. 36 µW

C. 6 mW

D. 36 mW

C

How long until the current is at a maximum?

Circuit description:

DC RL circuit with:

V1 = 12 V

R1 = 1 kΩ

L1 = 5 mH

A. 0 µs

B. 5 µs

C. 15 µs

D. 25 µs

D

A circuit has a resonant frequency of 455 kHz and a bandwidth of 57.2 kHz. Find the Q of the circuit.

A. 795

B. 0.795

C. 79.5

D. 7.95

D

A BUZ73L MOSFET has an “on” resistance of 0.4 Ω and is rated at 7 A. If the supply voltage is 9 V, what is the minimum resistance of a device in series that it can safely switch?

A. 1.286 Ω

B. 0.886 Ω

C. 0.486 Ω

D. 0.4 Ω

B

The current in a coil begins to fall at the rate of 6 A/s. If L = 840 mH, what emf is produced in the coil?

A. 2.25 V

B. 5.04 V

C. 4.05 V

D. 2.52 V

B

Determine the reluctance of a piece of mumetal of length 150 mm and cross-sectional area 1800 mm² when its relative permeability is 4000. Find also the absolute permeability of the mumetal.

A. 2 mH/m

B. 3 mH/m

C. 4 mH/m

D. 5 mH/m

D

Three concentric spheres of radii 4 cm, 6 cm, and 8 cm have charges of +8 pC, −6 pC, and +4 pC respectively. What is the potential 10 cm from the center?

A. 54 V

B. 0.45 V

C. 0.54 V

D. 45 V

C

Determine the total charge entering a terminal between t = 1 s and t = 2 s if the current passing the terminal is i = (3t² − t) A.

A. 4.5 C

B. 5.5 C

C. 6.5 C

D. 5.4 C

B

Given the circuit below, solve for current I and the power absorbed by the dependent source if V1 is the voltage across a 4 Ω resistor.

A. −2 A, −36 W

B. −2 A, −72 W

C. −8 A, −36 W

D. −8 A, −72 W

B

Inductances of 0.8 H and 0.11 H are connected in series, fields opposing. If the mutual inductance is 0.2 H, the total inductance is:

A. 0.15 H

B. 0.51 H

C. 0.30 H

D. 1.02 H

What is the bandwidth of the circuit?

A

If the load in the given circuit is 120 kΩ, what is the loaded output voltage?

B

What is the magnetomotive force in a 150-turn coil of wire with 2 A flowing through it?

A. 13.33 mAt

B. 300 At

C. 75 At

D. 152 At

B

What is the minimum contact rating for a relay required to switch a 1000 W, 230 V floodlamp?

A. 2.35 A

B. 3.35 A

C. 4.35 A

D. 5.35 A

C

A conductor carries a current of 20 A and is inclined at an angle of 30° to the direction of the field having a flux density of 0.9 T. If the length of the conductor in the field is 30 cm, calculate the force acting on the conductor.

A. 7.2 N

B. 2.7 N

C. 3.4 N

D. 4.3 N

B

A parallel plate capacitor has plates 0.15 mm apart and dielectric with relative permittivity of 3. Find the electric field intensity and the voltage between plates if the surface charge is 5 × 10⁻⁴ µC/cm².

A. 176 kV/m, 2.82 V

B. 188 kV/m, 2.82 V

C. 192 kV/m, 1.41 V

D. 168 kV/m, 1.41 V

B (28.2 V dapat)

What is the voltage across a 3 µF capacitor if the charge on one plate is 0.12 mC? How much energy is stored?

A. 1.2 mJ

B. 4.8 mJ

C. 2.4 mJ

D. 4.2 mJ

C

Given the capacitor network below, determine the voltage across capacitor C3.

A. 266.67 V

B. 133.33 V

C. 622.22 V

D. 311.11 V

A

A capacitor of 50 µF is connected in series with a resistor of 1000 Ω across a constant voltage source of 400 V. Determine the time constant.

A. 0.1 s

B. 0.005 s

C. 0.02 s

D. 50 ms

D

What is the range between f1 and f2 of an RLC circuit that resonates at 150 kHz and has a Q of 30?

A. 100.0 kHz to 155.0 kHz

B. 147.5 kHz to 152.5 kHz

C. 4500 kHz to 295.5 kHz

D. 149,970 Hz to 150,030 Hz

B

What is the total resistance of a circuit when R1 = 7 kΩ is in series with a parallel combination of R2 = 20 kΩ, R3 = 36 kΩ, and R4 = 45 kΩ?

A. 4 kΩ

B. 17 kΩ

C. 41 kΩ

D. 108 kΩ

B

What is the reluctance of a material that has a length of 0.045 m, a cross-sectional area of 0.015 m², and a permeability of 2500 µWb/At/m?

A. 833.33 µAt/Wb

B. 0.27 At/Wb

C. 1200 At/Wb

D. More information is needed in order to find the reluctance.