An electric circuit is a closed loop that allows electric current to flow, powered by a voltage source like a battery. In a series circuit, components are connected in a single loop, so current is the same throughout, but if one component fails, the whole circuit breaks. In a parallel circuit, components are connected on separate branches, so each gets the same voltage, and one failing doesn't stop the others.
Example
Old-style Christmas lights wired in series would all go out if one bulb blew, since the circuit was broken. Modern household wiring uses parallel circuits, so a broken light or appliance in one room doesn't cut power to the rest of the house.
Key terms
Current:
The flow of electric charge through a circuit, measured in amps.
Voltage:
The energy that pushes current through a circuit, measured in volts.
Series / parallel circuit:
A single-loop circuit (series) vs one with separate branches (parallel).
Questions
1. An electric circuit must form a:
Closed loop
Straight line only
Random shape with gaps
Perfect circle
2. Current is measured in:
Amps
Volts
Watts only
Metres
3. Voltage is measured in:
Volts
Amps
Litres
Kilograms
4. In a series circuit, components are connected:
In a single loop
On separate branches
Not connected at all
Randomly with no pattern
5. In a parallel circuit, components are connected:
On separate branches
In a single loop only
Not connected at all
Only one at a time
6. A battery in a circuit provides the:
Voltage (energy) to push current
Only light, nothing else
Only sound
The circuit's shape
7. If one bulb blows in a series circuit, the rest of the circuit:
Stops working too
Keeps working normally
Gets brighter
Is unaffected
8. If one bulb blows in a parallel circuit, the other branches:
Continue working
All stop working too
Get dimmer and turn off
Explode
9. Household wiring typically uses:
Parallel circuits
Series circuits only
No circuits at all
A single loop for the whole house
10. Why do old-style Christmas lights wired in series all go out if one bulb blows?
The circuit is a single loop, so a broken link stops all current flow
Each bulb has its own separate battery
The bulbs are not actually connected
Series circuits never break
11. In a series circuit, the current is:
The same throughout the circuit
Different at every point
Always zero
Impossible to measure
12. In a parallel circuit, each branch receives:
The same voltage
A different, unrelated voltage type
No voltage at all
Only current, never voltage
13. A switch in a circuit controls:
Whether the circuit is open (off) or closed (on)
The colour of the wires
The battery's size
Nothing important
14. Why might engineers choose a parallel circuit design for a house rather than a series one?
So that one broken appliance or light doesn't cut power to the rest of the house
Parallel circuits use less wire in every case
Series circuits are always safer
There is no practical difference between the two
15. Adding more bulbs in series to the same battery generally makes each bulb:
Dimmer, since voltage is shared across all bulbs
Brighter with no limit
Unaffected by the number of bulbs
Impossible to light at all
16. Adding more branches to a parallel circuit generally:
Does not dim existing branches, since each gets full voltage
Always dims every branch equally
Makes the circuit stop working entirely
Removes the need for a battery
17. Why is total resistance in a parallel circuit generally lower than in a series circuit with the same components?
Multiple paths let current flow more easily overall
Parallel circuits always have more resistance
Resistance has no relationship to circuit type
Series circuits have no resistance at all
18. A circuit with a short circuit (unintended low-resistance path) is dangerous mainly because it can cause:
Excessive current flow, leading to overheating or fire
The circuit to become completely safe
No current to flow at all
The voltage to disappear entirely
19. Why are fuses or circuit breakers included in household electrical systems?
To automatically cut off current if it becomes dangerously high
To make circuits permanently unusable
To increase voltage beyond safe levels
They serve no safety function
20. A combination circuit (using both series and parallel sections) might be used in real devices because:
Different sections can be designed for different purposes within one device
Combination circuits are always illegal
Only pure series or pure parallel circuits are ever used in practice
Combining circuit types has no practical benefit
21. Ohm's Law (V = IR) describes the relationship between:
Voltage, current and resistance
Only mass and weight
Only time and distance
Colour and brightness
Answer key (parent copy)
1. Closed loop
2. Amps
3. Volts
4. In a single loop
5. On separate branches
6. Voltage (energy) to push current
7. Stops working too
8. Continue working
9. Parallel circuits
10. The circuit is a single loop, so a broken link stops all current flow
11. The same throughout the circuit
12. The same voltage
13. Whether the circuit is open (off) or closed (on)
14. So that one broken appliance or light doesn't cut power to the rest of the house
15. Dimmer, since voltage is shared across all bulbs
16. Does not dim existing branches, since each gets full voltage
17. Multiple paths let current flow more easily overall
18. Excessive current flow, leading to overheating or fire
19. To automatically cut off current if it becomes dangerously high
20. Different sections can be designed for different purposes within one device