# Electric Circuits

Inquiry question: How do the processes of the transfer and the transformation of energy occur in electric circuits?

• investigate the flow of electric current in metals and apply models to represent current, including:
• πΌ = π/π‘
• investigate quantitatively the currentβvoltage relationships in ohmic and non-ohmic resistors to explore the usefulness and limitations of Ohmβs Law using:
• π = ππ
• π = πΌπ
• investigate quantitatively and analyse the rate of conversion of electrical energy in components of electric circuits, including the production of heat and light, by applying π = ππΌ and πΈ = ππ‘ and variations that involve Ohmβs Law
• investigate qualitatively and quantitatively series and parallel circuits to relate the flow of current through the individual components, the potential differences across those components and the rate of energy conversion by the components to the laws of conservation of charge and energy, by deriving the following relationships:
• π΄πΌ = 0 (Kirchhoffβs current law β conservation of charge)
• π΄π = 0 (Kirchhoffβs voltage law β conservation of energy)
• πseries = π1 + π2+. . . + πn
• 1/πparallel = 1/π1 + 1/π2+. . . + 1/πn
• investigate quantitatively the application of the law of conservation of energy to the heating effects of electric currents, including the application of π = ππΌ and variations of this involving Ohmβs Law

Learn.

Electrical circuits:

Kirchoff’s Law:

Memorize.

πseries = π1 + π2+. . . + πn

1/πparallel = 1/π1 + 1/π2+. . . + 1/πn

Questions.

Question 1. (8 marks)

a) Compare and contrast a circuit in series and parallel [3 marks]

b) Explain how voltage and current are measured in a circuit [2 marks]

c) Explain what current is in a circuit [3 marks]

Question 2. (8 marks)

a) Explain Kirchhoff’s circuit laws using equations in your response. [4 marks]

b) Outline an experiment which could be used to determine the validity of Kirchoff’s circuit laws

Question 3. (9 marks)

a) Determine the total resistance when 3 resistors are connected in parallel. Each resistor is 4 ohms and the current supplied is from two 9 V batteries connected in series. [3 marks]

b) Determine the total resistance when 3 resistors are connected in series. Each resistor is 4 ohms and the current supplied is from two 9 V batteries connected in series. [3 marks]

c) Determine the total resistance when 3 resistors are connected in parallel. Each resistor is 4 ohms and the current supplied is from two 9 V batteries connected in parallel. [3 marks]

Question 4. (4 marks) [extension]

Determine the total resistance if two resistors are connected in series, these are then put in parallel with another two resistors which were connected the same. What is the total resistance if each resistor was 6 ohms.