Topic 18 - Circuit, Parallel and Series

A diode can be used as a rectifier. What is the function of a rectifier?

• to convert a.c. into d.c.

• to convert d.c. into a.c.

• to reduce the size of an alternating current

• to reduce the size of a direct current

The electric light switch for a bathroom is sometimes fitted on the wall outside the bathroom. Why is this safer than fitting the switch on the wall inside the bathroom?

• The heat from the light affects the switch

• The person in the bathroom may be electrocuted if water enters the switch

• The switch is less likely to be damaged outside the bathroom

• The warm air in the bathroom causes the switch to overheat

A student has a set of 20 festive lights. The lights are wired in series and connected to the mains. One bulb burns out and all the lights go out. The student's parents ask her to find the faulty bulb and replace it. Where should the student begin?

• Anywhere, because the current will have been the same everywhere

• At the live end, because the current will have been greatest there

• At the middle, because the current will have been greatest there

• At the neutral end, because the current will have been greatest there

Which combination of identical resistors gives the lowest total resistance?

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Which graph shows the II characteristic for a semiconductor diode?

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The diagram shows part of an electric circuit. What is the current in the 2 Ω resistor?

• 0.6 A

• 1.2 A

• 3.0 A

• 6.0 A

In the circuit shown, at which point is the current smallest?

• A

• B

• C

• D

A battery is connected to two resistors. The p.d. across the battery is 12 V and the p.d across one resistor is 9 V. What is the p.d. across the other resistor?

• 3 V

• 6 V

• 9 V

• 21 V

The following circuit is set up. What is the reading on the ammeter?

• 0.33 A

• 0.50 A

• 0.67 A

• 1.0 A

The diagram shows part of an electric circuit. What is the effective resistance between X and Y?

• 1/20 Ω

• 1/5 Ω

• 5 Ω

• 20 Ω