Series and Parallel Circuits Potential Divider Circuit Laws

Series and Parallel Circuits Potential Divider Circuit Laws Direct Current Circuits

Series Circuit

Parallel Circuit

Examples • Question 15. 6, page 269 • For the same question, calculate – The current in each resistor – The pd across each resistor if the total voltage across the circuit is 100 V

Potential Divider • Remember Series • Fixed Resistor • Equation for output voltage

Potential Divider • Variable Resistor • Potentiometer • Rheostat • Light Dependent Resistor • Resistance depends on the amount of light on it • Thermistor • Resistance depends on the temperature

Light Dependent Resistor (LDR) • Resistance decreases as light intensity increases

Thermistor (NTC) • Resistance decreases as temperature increases

Potentiometer • Resistance varies with length of resistor

Circuit Laws • Kirchhoff’s Junction Rule – The total current in a junction is zero – Conservation of Charge • Current going in + • Current leaving -

Circuit Laws • Kirchhoff’s Loop Rule – The total voltage in a loop is zero – Conservation of Energy • For emf sources: • Traversing from – to +, positive • For resistors, V = IR: • If assumed or given current direction is the same as assumed or given loop direction, negative

Loop Rule

Example 1 • Find the current, I

Example 2 • Find the current, I • The internal resistance, r • The emf, ε

Example 3 • Find the current in the middle branch • The unknown emf