10.1 Practical circuits:
- Circuit symbols are used to represent components in circuit diagrams.
- Understanding and using circuit symbols is important for drawing and interpreting circuit diagrams.
- The electromotive force (e.m.f.) of a source is the energy transferred per unit charge when driving charge around a complete circuit.
- Differentiate between e.m.f. and potential difference (p.d.) based on energy considerations.
- The internal resistance of a source of e.m.f. affects the terminal potential difference in a circuit.
10.2 Kirchhoff's laws:
- Kirchhoff's first law states that the total current entering a junction in a circuit is equal to the total current leaving the junction, based on the principle of conservation of charge.
- Kirchhoff's second law (loop rule) states that the sum of the e.m.f.s and potential differences in any closed loop of a circuit is equal to zero, based on the principle of conservation of energy.
- Using Kirchhoff's laws, formulas for the combined resistance of resistors in series and parallel can be derived.
- The combined resistance of resistors in series is found by adding the individual resistances.
- The combined resistance of resistors in parallel is found using the formula 1/R = 1/R1 + 1/R2 + 1/R3 + ... (for two or more resistors).
- Kirchhoff's laws can be used to solve simple circuit problems.
10.3 Potential dividers:
- A potential divider circuit is a circuit that divides a voltage into smaller fractions using resistors.
- The principle of a potentiometer can be used to compare potential differences.
- A galvanometer is used in null methods to balance a circuit and measure unknown potential differences.
- Thermistors and light-dependent resistors (LDRs) can be used in potential dividers to provide a potential difference that depends on temperature and light intensity, respectively.