Principles of electrical science C&G 2

From a 50 metre cable drum, you have installed 13.6 metres of cable. What percentage of cable has been used?

• 3.8%

• 72.8%

• 27.2%

• 65%

Answer explanation

To find the percentage of cable used, divide the length used (13.6m) by the total length (50m) and multiply by 100. (13.6/50) * 100 = 27.2%

An insulation resistance tester is used to record the following values: 55MΩ, 72MΩ, 55MΩ, 18.5Ω, 10 MΩ and 89MΩ. What is the mean of these values?

• 49.9MΩ

• 89MΩ

• 55MΩ

• 18.5MΩ

Answer explanation

To find the mean, add all values together and divide by the total number of values. (55+72+55+18.5+10+89)/6 = 49.9MΩ. Therefore, the mean of these values is 49.9MΩ.

The SI unit for resistivity is?

• Ohm

• Ωm

• R

• Ω

Answer explanation

The SI unit for resistivity is represented by the symbol Ωm, where Ω is the unit for resistance and m is the unit for length.

Potential Difference is measured in?

• Amps

• Volts

• Newton’s

• Joule’s

Answer explanation

Potential Difference is measured in Volts, not Amps, Newton’s, or Joule’s.

In the SI system, time is measured in?

• Hours

• Minutes

• Seconds

• Kelvin’s

Answer explanation

In the SI system, time is measured in seconds.

Which instrument would be used to measure the resistance of a circuit?

• Ohm meter

• Conductance meter

• Continuity meter

• Amp meter

Answer explanation

An ohm meter is used to measure the resistance of a circuit, making it the correct choice for this question.

The SI unit for Capacitance is the?

• Volt

• Henry

• Hertz

• Farad

Answer explanation

The SI unit for Capacitance is the Farad.

A load generates a force of 300 Newton’s. Calculate the mass of the load.

• 3.6 kg

• 3060 kg

• 306 kg

• 30.6 kg

Answer explanation

To calculate the mass, divide the force (300 N) by the acceleration due to gravity (9.81 m/s^2) to get 30.6 kg.

Lifting a load an electric motor uses 180,000 Joules of energy in 1 ½ minutes. What is the power rating of the motor?

• 500 W

• 1 kW

• 1.5 kW

• 2 kW

Answer explanation

The power rating of the motor can be calculated using the formula Power = Energy / Time. Substituting the given values, Power = 180,000 J / 90 s = 2 kW.

Crowbars are an example of what type of lever?

• Class 1

• Class 2

• Class 3

• Class 4

Answer explanation

Crowbars are an example of Class 1 lever where the fulcrum is located between the effort and the load, making it easier to lift heavy objects.