Electrical Quantities Continued
Overview
Every time you switch on a light, charge is pushed around a circuit by a source, gives up energy in the bulb, and returns for more. The push is the electromotive force, the energy given up per coulomb is the potential difference, and the opposition to the flow is the resistance. Master these three and you can analyse and cost almost any circuit.
In this topic you will define e.m.f. and potential difference, use voltmeters, measure and calculate resistance, and link power and energy to current and voltage. You will sketch the current-voltage graphs of a resistor, a lamp and a diode, and learn to work out the cost of running appliances in kilowatt-hours.
Objectives
- [Core] Know that electric current is related to the flow of charge
- [Core] Know that electric current in metals is related to the flow of electrons
- [Core] Describe the use of ammeters (analogue and digital) with different ranges
- [Core] Know the difference between direct current (d.c.) and alternating current (a.c.)
- [Core] Describe the voltage of the source as the cause of current in the circuit
- [Core] Know that the voltage of the source is shared between the components in a series circuit
- [Core] Describe the use of voltmeters (analogue and digital) with different ranges
- [Core] Recall and use the equation for resistance V R = I
- [Supplement] Define electric current as the charge passing a point per unit time; recall and use the equation Q I = t
- [Supplement] Describe electrical conduction in metals in terms of the movement of delocalised (mobile) electrons
- [Supplement] State that conventional current is from positive to negative and that the flow of electrons is from negative to positive
- [Supplement] Define electromotive force (e.m.f.) as the electrical work done by a source in moving a unit charge around a complete circuit
- [Supplement] Know that e.m.f. is measured in volts (V)
- [Supplement] Define potential difference (p.d.) as the work done by a unit charge passing between two points in a circuit
- [Supplement] Know that the p.d. between two points is measured in volts (V)
- [Supplement] Recall and use the following relationship for a metallic electrical conductor: (a) resistance is directly proportional to length (b) resistance is inversely proportional to cross-sectional area
Lesson Note
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Lesson Evaluation
Congratulations on completing the lesson on Electrical Quantities Continued. Now that youve explored the key concepts and ideas, its time to put your knowledge to the test. This section offers a variety of practice questions designed to reinforce your understanding and help you gauge your grasp of the material.
You will encounter a mix of question types, including multiple-choice questions, short answer questions, and essay questions. Each question is thoughtfully crafted to assess different aspects of your knowledge and critical thinking skills.
Use this evaluation section as an opportunity to reinforce your understanding of the topic and to identify any areas where you may need additional study. Don't be discouraged by any challenges you encounter; instead, view them as opportunities for growth and improvement.
- The resistance of a component carrying 2 A with 12 V across it is: A. 24 ohm B. 6 ohm C. 0.17 ohm D. 10 ohm Answer: B
- A voltmeter should be connected: A. in series with the component B. in parallel with the component C. before the cell only D. it does not matter Answer: B
- The I-V graph of a resistor of constant resistance is: A. a curve flattening off B. a straight line through the origin C. zero one way only D. a horizontal line Answer: B
- A 60 W lamp runs for 1 hour. The energy used is: A. 60 J B. 0.06 kW h C. 60 kW h D. 3600 kW h Answer: B
- 1 kilowatt-hour is equal to: A. 1000 J B. 3600 J C. 3.6 MJ D. 60 J Answer: C
Available on the Green Bridge App
Download the Green Bridge CBT app on your phone or computer to access full lesson notes, practice questions, and more.
Available on the Green Bridge App
Download the Green Bridge CBT app on your phone or computer to access full lesson notes, practice questions, and more.
Recommended Books
Practice Mock Questions
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