Current, voltage and resistance

A student uses a length of wire as a resistor. He makes a second resistor from the same material.

To be certain of making a second resistor of higher resistance, he should use a piece of wire that is:

• longer and thicker.

• longer and thinner.

• shorter and thicker.

• shorter and thinner.

The table describes four different resistance wires.

They are all made from the same metal.

Which wire has the smallest resistance?

• A

• B

• C

• D

The circuit shown contains a battery, a 6.0 Ω resistor and two meters X and Y.

One meter records current and one meter records potential difference.

• meter X : 2.0 A

  meter Y : 12.0 V

• meter X : 2.0 V

  meter Y : 1.0 A

• meter X : 12.0 A

  meter Y : 2.0 V

• meter X : 12.0 V

  meter Y : 2.0 A

• most brightly: W

  least brightly: Y

• most brightly: W

  least brightly: Z

• most brightly: X

  least brightly: Y

• most brightly: X

  least brightly: Y

The diagram shows a circuit with a 3.0Ω and a 2.0 Ω resistor connected in parallel.

The switch is open, and the ammeter reads 2.0 A.

The switch is now closed and the ammeter reads the total current in both resistors.

What is the ammeter reading with the switch closed?

• 1.2 A

• 3.0 A

• 4.0 A

• 5.0 A

Which equation can be used to calculate the resistance R of a resistor?

• V = I / R

• I = V x R

• R = V x I

• V = I x R

The diagrams show four current-voltage graphs.

Which two graphs show the characteristics of an ohmic resistor and of a filament lamp?

• ohmic resistor : W

  filament lamp : Y

• ohmic resistor : X

  filament lamp : Y

• ohmic resistor : W

  filament lamp : Z

• ohmic resistor : X

  filament lamp : Z

The resistance of a wire depends on its length l and on its cross-sectional area A.

The resistance is:

• directly proportional to l and directly proportional to A.

• directly proportional to l and inversely proportional to A.

• inversely proportional to l and directly proportional to A.

• inversely proportional to l and inversely proportional to A.

Which symbols are used for the units of current and of resistance?

• A

• B

• C

• D

There is a current of 2.0A in a resistor for 30 s.

The potential difference (p.d.) across the resistor is 12V.

How much energy is transferred in the resistor?

• 1.25 J

• 5.0 J

• 180 J

• 720 J