For which one of these processes is Direct Current essential, and will not work with alternating current?

- Heating
- Lighting
- Turning a motor
- Electrolysis

AC is more easily distributed than DC. This is because:

- AC can be transmitted using lighter wires.
- DC needs wires to be totally insulated, while AC wires can be bare, hung from insulator on pylons.
- AC can be transformed from a low voltage to a high voltage and back again with a tranformer. DC cannot.
- Wires have less resistance if they are carrying AC

An alternating wave form rises from zero volts to maximum volts, through zero, to maximum negative voltage, back to zero. This is shown on a CRO. Which one of the statements is true?

- This is called a cycle and the distance between successive points that are in phase represents the wavelength.
- This is called a cycle and the distance between successive points that are in phase represents the period.
- This is called a cycle and the distance between successive points that are in phase represents the frequency.
- The CRO is faulty as AC waveforms do not behave like this.

The voltage in an AC waveform varies sinusoidally. Which one of these statements is correct for the current through a resistor?

- The current stays at a constant value.
- The current varies as a square wave in phase with the voltage.
- The current varies sinusoidally 90 degrees out of phase with the voltage.
- The current varies sinusoidally in phase with the voltage.

Which one of these statements is correct about the rms value of an alternating voltage?

- It is twice the value of the peak voltage.
- It is half the value of the peak voltage and is the same value of the equivalent DC voltage
- It is the value of the peak voltage divided by root 2 and is the same value of the equivalent DC voltage
- It is root 2 times the value of the peak voltage and is the same value of the equivalent DC voltage

What is the peak voltage of the 230 V rms mains

- 115 V
- 163 V
- 230 V
- 325 V

A heater takes 10 A rms from the 230 V rms mains. What is its power?

- 1630 W
- 2300 W
- 3250 W
- 4600 W

During the forward half cycle, when the alternating voltage is positive, the power has a positive value. Which one of these statements about the power in the reverse half cycle is also true?

- The power has zero value.
- During the reverse half cycle, the current is positive, so the power has a neagtive value.
- During the reverse half cycle, the current is negative, so the power has a negative value.
- During the reverse half cycle, the current is negative, so the power has a positive value.

Which one of these statements BEST describes the use of a CRO as a measuring instrument?

- The CRO can be used to measure frequency, but can only be used to measure voltage.
- The CRO can be used to measure frequency, but can be used to measure voltage, and in parallel with a known resistor, can measure current.
- The CRO can be used to measure frequency, but can be used to measure voltage, and in series with a known resistor, can measure current.
- The CRO only displays the waveform. No meaningful electrical measurements can be made from it.

Which one of the following statements is true about the controls on a CRO?

- Voltage is measured on the vertical axis and the sensitivity is changed with the y-gain control. Time is measured on the horizontal axis and the sensitivity is changed with the time base.
- Voltage is measured on the horizontal axis and the sensitivity is changed with the y-gain control. Time is measured on the vertical axis and the sensitivity is changed with the time base.
- Voltage is measured on the vertical axis and the sensitivity is changed with the time base. Time is measured on the horizontal axis and the sensitivity is changed with the y-gain control
- Voltage is measured on the horizontal axis and the sensitivity is changed with the time base. Time is measured on the vertical axis and the sensitivity is changed with the y-gain control