Electricity Exam Review

Magnetic shielding used to protect electrical wires from outside magnetic forces:

• Block the magnetic field

• provide an alternative path for the magnetic field

• generate an equal and opposite magnetic field to protect the wires

• nothing, they are a scam created by the wire industry

• none of the above

Electrical energy is billed to consumers in which of the following units?

• megawatts

• kilowatt-amps

• kilowatt-hours

• joules

Calculate the total resistance for the circuit shown.

• 40 Ω

• 13.33 Ω

• 17.14 Ω

• 20 Ω

• 130 Ω

Which of these is a variable resistor that is used to vary the level of an AC or DC voltage?

• rheostat

• potentiometer

• wire-wound resistor

• carbon filament resistor

• chip resistor

When a resistor has a 2-W rating, this means that it:

• always dissipates exactly 2 W of power

• dissipates 2 W of power when connected to a 120 VAC circuit

• can safely dissipate 2 W, or less, of power

• always provides 2 W of power

The lines of force in a magnetic field...

• never cross each other

• form closed loops

• follow the path of least resistance, such as soft iron

• all of the above

Which of these does not normally have a demagnetizing effect?

• heat

• AC applied to a coil

• mechanical vibration

• DC applied to a coil

Motor-winding conductors often use

• neoprene insulation

• a baked-on enamel insulation

• type TWH insulation

• type TW insulation

If a compass is placed at the center of a bar magnet, the compass needle...

• points to the geographic north pole

• aligns itself parallel to the bar

• aligns itself perpendicular

• points to the geographic south pole

Assuming each one of the resistors has a resistance of 100 Ω, find the combined total resistance of each circuit.

• series 200 Ω, parallel 100 Ω, series-parallel 200 Ω

• series 50 Ω, parallel 100 Ω, series-parallel 200 Ω

• series 200 Ω, parallel 50 Ω, series-parallel 100 Ω

• series 100 Ω, parallel 200 Ω, series-parallel 50 Ω