Open the simulation Print this page on A4.

Student worksheet

1. Current, P.D. & Resistance

Name:

Class: ______ Date: ________

Open the simulation and work through each chapter. Write your prediction before you run the test.

a. Charge and current

Predict

The ammeter reads 0.50 A. Predict the charge passing in 20 s.

My prediction (and why)

What happened

Was I right? If not, what was wrong with my thinking?

Test: recording table

I / A	t / s	Q / C	Q ÷ t / A

Pattern I found:

Challenge

Set the rheostat so that exactly 6.0 C of charge passes the ammeter every 12 s.

My solution

Exam practice

A current of 0.40 A flows in a lamp for 2.0 minutes. Calculate the charge that passes through the lamp. [2]
90 C of charge flows through a heater in 30 s. Calculate the current. [1]
Which statement about current in a metal wire is correct? [1]
A Conventional current and electron flow are in the same direction
B Electrons flow from the negative terminal of the cell round the circuit to the positive terminal
C Current is the energy carried by each electron
D Current is measured with a voltmeter connected in parallel
Answer: ____

b. E.m.f. and potential difference

Predict

Four 1.5 V cells in series; the third is reversed. Predict V_cells.

My prediction (and why)

What happened

Was I right? If not, what was wrong with my thinking?

Test: recording table

Cells forwards	Cells reversed	e.m.f. / V	I / A

Pattern I found:

Challenge

Make the lamp current exactly 0.25 A (the lamp is 12 Ω). Use the cell settings.

My solution

Exam practice

36 J of energy is transferred when 3.0 C of charge passes through a lamp. Calculate the p.d. across the lamp. [2]
A 9.0 V battery drives 0.20 A round a circuit for 50 s. Calculate the work done by the battery. [2]
Three 1.5 V cells are connected in series, but one faces the opposite way to the other two. What is the total e.m.f.? [1]
A 0 V
B 1.5 V
C 3.0 V
D 4.5 V
Answer: ____

c. Resistance

Predict

6.0 V battery, 12 Ω resistor, 0.50 A. Predict the current and battery p.d. with a 30 Ω resistor instead.

My prediction (and why)

What happened

Was I right? If not, what was wrong with my thinking?

Test: recording table

Load / Ω	V / V	I / A	V ÷ I / Ω

Pattern I found:

Challenge

Component X is hidden. Use the meters (change the battery if you like) to find its resistance, then enter it.

My solution

Exam practice

The p.d. across a resistor is 4.5 V and the current through it is 0.15 A. Calculate its resistance. [2]
A 6.0 V battery is connected to a 24 Ω resistor. Calculate the current. [1]
The same ideal 6.0 V battery is connected in turn to a 10 Ω resistor and to a 20 Ω resistor. Which statement is correct? [1]
A The current is the same both times
B The battery’s e.m.f. is the same; the current halves with 20 Ω
C The e.m.f. doubles with 20 Ω
D The current doubles with 20 Ω
Answer: ____

d. I–V characteristics

Predict

Sketch the I–V graph you expect for a filament lamp from −6 V to +6 V.

My prediction (and why)

What happened

Was I right? If not, what was wrong with my thinking?

Test: recording table

V / V	I / A	R = V/I / Ω

Pattern I found:

Challenge

Component Y is hidden. Plot its I–V graph and decide what it is.

My solution

Exam practice

Which I–V graph is a straight line through the origin? [1]
A Filament lamp
B Metal wire at constant temperature
C Diode
D Thermistor as it warms up
Answer: ____
Why does the I–V graph of a filament lamp curve? [1]
A The current is used up in the filament
B The filament’s temperature rises, so its resistance increases
C The lamp only conducts in one direction
D The p.d. across the lamp stays constant
Answer: ____
A filament lamp carries 0.20 A at 1.0 V and 0.50 A at 6.0 V. Calculate its resistance at 6.0 V. [1]

e. Resistance of a wire

Predict

A wire twice as long and twice the area (same material). Predict its resistance compared with 2.20 Ω.

My prediction (and why)

What happened

Was I right? If not, what was wrong with my thinking?

Test: recording table

Material	L / m	A / mm²	θ / °C	R / Ω

Pattern I found:

Challenge

Using nichrome wire at 20 °C, choose a length and area so that the ammeter reads 0.75 A from the 1.5 V cell.

My solution

Exam practice

A wire of length 0.80 m has a resistance of 4.0 Ω. What is the resistance of 2.0 m of the same wire? [2]
A wire has a resistance of 6.0 Ω. Another wire of the same material and length has three times the cross-sectional area. Calculate its resistance. [1]
Wire P has length L and diameter d. Wire Q, of the same material, has length L and diameter 2d. What is the ratio resistance of Q : resistance of P? [1]
A 1 : 4
B 1 : 2
C 2 : 1
D 4 : 1
Answer: ____

f. Thermistor and LDR

Predict

Thermistor heated from 20 °C to 80 °C. Predict the change in the ammeter reading.

My prediction (and why)

What happened

Was I right? If not, what was wrong with my thinking?

Test: recording table

θ / °C or light / %	V / V	I / mA	R / Ω

Pattern I found:

Challenge

Set the temperature of the thermistor so that the ammeter reads 15 mA (±0.3 mA).

My solution

Exam practice

How does the resistance of an NTC thermistor change as it is heated? [1]
A It increases steadily
B It decreases
C It stays the same
D It increases, then decreases
Answer: ____
An LDR is covered so that no light reaches it. What happens to its resistance and to the current through it from a fixed supply? [1]
A Resistance rises; current falls
B Resistance falls; current rises
C Both rise
D Both fall
Answer: ____
A thermistor connected to a 6.0 V supply carries 2.0 mA. Calculate its resistance in kΩ. [2]