Alternating Current

The graphs shows how a potential difference (p.d.) varies with time.

Which of the following is correct?

• the frequency is 4.5 Hz

• the peak value is 4.0 V

• the period is 0.20 s

• the root mean square value of p.d. is 1.0 V

A wire carries an alternating current of peak value 3 A. Which of the following is the root-mean-square value of this current?

• 1.5 A

• 2.1 A

• 4.2 A

• 9.0 A

Which statement about alternating current is incorrect?

• The rms current is the value of the direct current that would produce an equivalent heating effect

• The peak value of an alternating current is half of the peak-to-peak value of current

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• the rms current is greater than the peak current

Many household appliances are connected to a 230 V rms mains supply.

What is the peak voltage of a household's mains supply?

• 0 V

• 115 V

• 230 V

• 325 V

A sinusoidal current has a time period T. The peak current is I0 and the rms current I flows in a resistor such that the mean power dissipated in the resistor is P. Which of the following statement is correct?

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An alternating current I in amps varies with time t in seconds according to the equation:
I = 3 sin (50t)

What is the mean power dissipated by the alternating current in a resistive load of 10 ohm?

• 21 W

• 30 W

• 44 W

• 810 W

A sinusoidal alternating current flow through a resistor of 50 kiloohm, as shown in the image below:

which graph correctly shows the power dissipated in the resistor?

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