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1.5Unit 9: Electricity and circuits

Adding or removing components — Cambridge Checkpoint Physics 0893 Revision Notes & Topical Questions

5 min read 9 parts Lesson 5 of 5 1 quiz

📚 Cambridge Checkpoint Physics 0893 Hub / Topical Revision
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Lesson summary

1.5 Adding or removing components — CHECKPOINT PHYSICS 0893 notes: Explain how adding or removing cells and lamps changes the current in a series circuit.Train model — electrons in a series circuit move like a train, so all parts move at the same speedSame current — an ammeter re…

  • More cells
  • Fewer cells
  • Energy transfer
  • Slower flow
  • More lamps
  • Fewer lamps

Section 1 of 9Current in a series circuit

Train model
  • Train model electrons in a series circuit move like a train, so all parts move at the same speed
Same current
  • Same current an ammeter reads the same wherever it is placed in a series circuit
Order
  • Order the same components in a different order give the same current

Section 2 of 9Adding or removing cells

Energy
  • Energy a cell stores chemical energy that is changed to electrical energy in a complete circuit
More cells
  • More cells there is more electrical energy, so the current is larger
Fewer cells
  • Fewer cells there is less electrical energy, so the current is smaller
Two cells
  • Two cells with all other components identical, two cells give double the current of one cell and the lamp is brighter
Care
  • Care too many cells can damage lamps and make wires hot

Section 3 of 9Adding or removing lamps

1Energy transfer
  • Energy transfer electrons carry electrical energy and give some to the lamp, which changes it into light and thermal energy
2Slower flow
  • Slower flow a lamp makes the electrons move more slowly all the way round the circuit
3More lamps
  • More lamps the current decreases and the lamps are dimmer
4Two lamps
  • Two lamps with identical parts, two lamps transfer twice as much energy and halve the current
5Fewer lamps
  • Fewer lamps the current increases

Section 4 of 9Increasing and decreasing the current

To increase
  • To increase add a cell or remove a lamp
To decrease
  • To decrease remove a cell or add a lamp
Condition
  • Condition all other components are kept the same

Section 5 of 9Measuring current when components change

1
Build a series circuit with one cell, one lamp, an ammeter and a switch.
2
Close the switch and record the current.
3
Add a second lamp and record the current, then add a third lamp and record again.
4
Open the switch before each change.
5
Repeat the circuit with one, two and three cells and record the current each time.
6
Display the results in a table or chart and conclude how each change affects the current.

Section 6 of 9Safety rules

Lamps
  • Lamps do not remove all the lamps from a circuit, leaving only the cells
Ammeter
  • Ammeter do not connect an ammeter directly to cells without lamps
Bright lamp
  • Bright lamp switch off immediately if a lamp appears too bright

Section 7 of 9More from the specification

More from the specification
Current modulation in series circuits
  • Current modulation in series circuits inserting additional series resistors provides an experimental means to decrease total circuit current.
Adding cells in series
  • Connecting additional identical cells in series increases total electrical push (voltage), driving a greater current through the circuit.
Adding lamps in series
  • Adding more identical lamps increases total electrical resistance, reducing the current and causing each lamp to dim.
Removing circuit components
  • Disconnecting any single component in a simple series circuit breaks the continuous loop, extinguishing all other connected devices.
Electrical resistance concept
  • The opposition to the flow of electric charge;
    • higher resistance reduces current for a given supply voltage (I = V / R).
Conductor
  • Material that allows current to flow.
Circuit diagram
  • Drawing of a circuit using standard symbols.

Section 8 of 9Key terms

TermMeaning
Series circuitCircuit with components connected one after another in a single loop.
CurrentFlow of electrons measured in amps.
DimmerNot shining as brightly.
ComponentPart of a circuit such as a cell, lamp or switch.
Electrical energyEnergy carried by electrons in a circuit.

Section 9 of 9Exam technique

1
Thinking adding lamps increases the current — in a series circuit more lamps decrease the current.
2
Thinking current is different in different parts of a series circuit — it is the same everywhere.
3
Thinking more cells make the lamp dimmer — more cells increase current and brightness.
4
Connecting an ammeter directly across cells — it needs lamps in the circuit to protect it.

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