Summary
Electrical quantities such as current, potential difference, and resistance are fundamental to understanding circuits. Current is the flow of electric charge, potential difference is the energy required to move a charge between two points, and resistance is how difficult it is to push a current through a circuit.
- Current — the rate of flow of electric charge. Example: Measured in Amperes (A).
- Potential Difference — the energy required to move a charge from one point to another. Example: Measured in Volts (V).
- Resistance — the measure of how difficult it is to push a current through a circuit. Example: Measured in Ohms (Ω).
- Ohm's Law — states that the current through a conductor is directly proportional to the voltage across it. Example: V = IR, where V is voltage, I is current, and R is resistance.
- Thermistor — a temperature-dependent resistor. Example: Used in fire alarms.
- Light Dependent Resistor (LDR) — a resistor that changes resistance with light intensity. Example: Used in street lights.
Exam Tips
Key Definitions to Remember
- Current: The flow of electric charge.
- Potential Difference: The energy required to move a charge between two points.
- Resistance: The difficulty in pushing a current through a circuit.
Common Confusions
- Confusing potential difference with current.
- Misunderstanding the direction of current flow in circuits.
Typical Exam Questions
- What is Ohm's Law? Answer: Ohm's Law states that the current through a conductor is directly proportional to the voltage across it.
- How does a thermistor work? Answer: A thermistor's resistance decreases as temperature increases.
- What happens to resistance in a series circuit? Answer: The total resistance is the sum of the individual resistances.
What Examiners Usually Test
- Understanding of Ohm's Law and its application.
- Ability to calculate total resistance in series and parallel circuits.
- Knowledge of how thermistors and LDRs function.
