Electrical Engineering

Give the name of materials which contain lots of free electrons.

• insulators

• conductors

• semiconductors

• None of the above

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NGSS.HS-PS2-6

What are the basic components of a simple electric circuit?

• energy source

• connecting wires

• switch

• All the above

Which of the following is true of electrical forces?

• Like charges attract, unlike charges repel.

• Electrical forces are produced by electrical charges.

• Positive and negative charges can combine to produce the third type

• Electrical forces are weaker than gravitational forces.

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NGSS.HS-PS2-4

NGSS.HS-PS2-5

NGSS.HS-PS3-5

Which of the following is not an electrical classification of materials?

• Semiconductors

• Semi-insulators

• Insulators

• Conductors

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NGSS.HS-PS2-5

Explain one reason why AC is used in preference to DC for most electrical distribution in the UK.

• AC can be easily converted to different voltages using transformers

• DC is more efficient than AC

• AC is more expensive than DC

• DC is safer to transmit over long distances

List three types of AC motor controller.

• Soft start, Rotor resistance, Direct online

• Pulse-width modulation, Voltage controller, and Slip ring induction

• Direct torque control, Slip ring induction, and Synchronous motors

• Frequency converter, Pulse-width modulation, and Brushless DC

Tags

NGSS.HS-PS2-5

NGSS.HS-PS3-3

Determine the neutral current within a three-phase circuit where the current for each phase is L1 = 80 A, L2 = 60 A and L3 = 40 A.

• 36 A

• 40A

• 42A

• 38A

Why must electric immersion heaters in hot water cylinders have a thermal cut-out within?

• To prevent the water from freezing

• To regulate the water temperature for energy efficiency

• To prevent the water from overheating and potentially causing damage or injury

• To monitor the water level in the cylinder

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NGSS.HS-ETS1-3

List three different devices that can provide overcurrent protection.

• Fuse, Circuit Breaker, Ground Fault Circuit Interrupter

• Resistor, Capacitor, Inductor

• Transistor, Diode, Transformer

• Voltage Regulator, Amplifier, Oscillator

Explain why three-phase motor circuits do not usually include a neutral conductor.

• Because all three phases are balanced there will be no neutral current and thus a conductor is not required. 

• Due to the high cost of additional wiring for the neutral conductor.

• Neutral conductors are only omitted in single-phase circuits, not three-phase circuits.

• It is a common misconception; three-phase motor circuits always include a neutral conductor.

Answer explanation

The three phases carry the return currents of each other, eliminating the need for a neutral conductor.