🧰 You need: pen, pencil, ruler, calculator. Time: 45 minutes. Course: Combined and Separate. Draw every wire and symbol with a ruler and pencil.
Information – read this first
| Component | How to draw the symbol |
|---|---|
| Cell | A long thin line and a short thick line, side by side (the long line is +) |
| Battery | Two or more cells joined together |
| Switch (open) | A gap in the wire with a short line hinged up at an angle |
| Lamp | A circle with a cross (X) inside |
| Resistor | A small rectangle |
| Variable resistor | A rectangle with a diagonal arrow through it |
| Fuse | A rectangle with a line running through it lengthways |
| Ammeter | A circle with A inside |
| Voltmeter | A circle with V inside |
| Diode | A triangle pointing at a short line across the wire |
| LED | A diode symbol with two small arrows pointing away from it |
| LDR | A rectangle inside a circle, with two small arrows pointing in |
| Thermistor | A rectangle with a diagonal line through it that has a short flat “foot” at the bottom |
- An ammeter measures current (A). It goes in series – in the loop.
- A voltmeter measures potential difference (V). It goes in parallel – across the component.
- Series circuit: one loop. The current is the same everywhere. The potential difference is shared. Total resistance = R₁ + R₂.
- Parallel circuit: more than one branch. The potential difference across each branch is the same. The current splits between the branches. Total resistance is less than the smallest resistor.
- V = IR (potential difference = current × resistance) P = VI (power = potential difference × current) Q = It (charge = current × time)
What to do
- (2 min) Write the title Circuit Symbols and Circuits and today’s date. Underline both with a ruler.
- (12 min) Rule a table with two columns: Component and Symbol. Draw all 13 symbols from the table above in pencil with a ruler.
- (8 min) Draw a series circuit with: a cell, a closed switch, a lamp and a resistor all in one loop, an ammeter in the loop, and a voltmeter across the lamp. Draw the wires as straight lines with square corners.
- (8 min) Draw a parallel circuit with: a battery, two lamps on separate branches, an ammeter in the main wire next to the battery, and a voltmeter across one lamp.
- (2 min) Under each circuit, copy the rules for current and potential difference from the information box.
- (10 min) Write the heading Calculations. Copy the worked example, then do Q1–Q6.
- (3 min) Check your answers and correct in a different colour.
Calculations
Worked example: A current of 0.5 A flows through a 12 Ω resistor. Find the potential difference.
V = IR = 0.5 × 12 = 6 V
Q1 A current of 2 A flows through a 6 Ω resistor. Calculate the potential difference.
Show answer
V = 2 × 6 = 12 V
Q2 A 4 Ω resistor has a potential difference of 12 V across it. Calculate the current.
Show answer
I = V ÷ R = 12 ÷ 4 = 3 A
Q3 A lamp on the 230 V mains takes a current of 0.5 A. Calculate its power.
Show answer
P = VI = 230 × 0.5 = 115 W
Q4 A 2300 W kettle runs on 230 V. Calculate the current.
Show answer
I = P ÷ V = 2300 ÷ 230 = 10 A
Q5 A 4 Ω and a 6 Ω resistor are in series with a 5 V battery. Calculate the total resistance and the current.
Show answer
Total R = 4 + 6 = 10 Ω. I = V ÷ R = 5 ÷ 10 = 0.5 A
Q6 A current of 0.2 A flows for 60 s. Calculate the charge that flows.
Show answer
Q = It = 0.2 × 60 = 12 C
⭐ Challenge
In your parallel circuit, one lamp breaks. Explain what happens to the other lamp. Then explain why the lights in a house are wired in parallel, not in series.
Show answer
The other lamp stays on, because it is on its own branch – there is still a complete loop through it, with the full potential difference across it. House lights are in parallel so each light can be switched on and off on its own, each gets the full mains potential difference, and one broken bulb doesn’t turn the others off.
