1.1. A student investigates resistors connected in series in an electrical circuit. The student has

• a 3.0 V battery

• a 22 Ω resistor

• a resistor marked X.

The student does not know the value of the resistor marked X.

The student decides to measure the potential difference (voltage) across resistor X.

Figure 15 shows the circuit that the student connected.

Figure 15

The circuit is connected incorrectly.

Describe how the student should correct the mistake.

1.2. The student corrects the mistake.

The voltage across resistor X is 2.1 V.

The circuit is connected to a 3 V battery.

(i) State the value of the voltage across the 22 Ω resistor.

voltage across 22 Ω resistor = ...................................... V [1]

ii) The current in resistor X is 0.041 A.

The voltage across resistor X is 2.1 V.

Show that the resistance of resistor X must be about 50 ohms.

Use the equation

V = I × R

[2]

iii) Calculate the power in resistor X when the voltage across X is 2.1 V and the current in resistor X is 0.041 A.

power = .............................................................. W [2]

iv) Calculate the overall resistance of the 22 ohm resistor and resistor X.

overall resistance = ................................................ Ω [2]

v) The current in the circuit is 0.041 A.

The voltage across the battery is 3.0 V.

Calculate the energy transferred in 2 minutes.

Use the equation

E = I × V × t

energy = .................................................... J [2]