Study Notes
A DC Circuit is an electrical circuit that allows current to flow in one direction only. It includes components like resistors, thermistors, and light-dependent resistors (LDRs) arranged in series or parallel.
- Current — the flow of electric charge in a circuit. Example: In a series circuit, the current is the same throughout.
- Potential Difference (Voltage) — the work done to move a charge between two points in a circuit. Example: In a parallel circuit, the potential difference is the same across each branch.
- Resistance — a measure of how much a component reduces the current flow. Example: Total resistance in series is the sum of individual resistances.
- Thermistor — a resistor whose resistance decreases as temperature increases. Example: Used in fire alarms to detect temperature changes.
- Light-Dependent Resistor (LDR) — a resistor whose resistance decreases as light intensity increases. Example: Used in cameras to adjust shutter speed based on light conditions.
Exam Tips
Key Definitions to Remember
- Current is the flow of electric charge.
- Potential difference is the work done per unit charge.
- Resistance is the opposition to the flow of current.
- A thermistor decreases in resistance with increasing temperature.
- An LDR decreases in resistance with increasing light intensity.
Common Confusions
- Confusing series and parallel circuit rules for current and voltage.
- Misunderstanding how resistance changes in thermistors and LDRs.
Typical Exam Questions
- What is the current in a series circuit? The current is the same at every point in a series circuit.
- How does a thermistor behave with temperature change? A thermistor's resistance decreases as temperature increases.
- How do you calculate total resistance in parallel? Use the formula 1/Rtotal = 1/R1 + 1/R2 + 1/R3.
What Examiners Usually Test
- Understanding of series and parallel circuit rules.
- Ability to draw and interpret circuit diagrams.
- Application of Ohm's Law and resistance calculations.