Energy And Voltage In Circuits
Overview
Every electrical device you use, from a phone charger to a hospital ventilator, relies on charges moving through circuits and transferring energy along the way. Understanding how current, voltage and resistance relate to each other is the key to predicting what any circuit will do, and it is one of the most heavily examined areas of your Edexcel course.
You will learn the equations that connect charge, current and time, explore how voltage measures energy transfer per coulomb, and master Ohm's law. You will also discover how different components behave, from resistors that obey a straight-line rule to diodes that only conduct one way, and see why homes use parallel circuits while fairy lights use series.
Objectives
- Explain why a series or parallel circuit is more appropriate for particular applications, including domestic lighting
- Understand how the current in a series circuit depends on the applied voltage and the number and nature of other components
- Describe how current varies with voltage in wires, resistors, metal filament lamps and diodes, and how to investigate this experimentally
- Describe the qualitative effect of changing resistance on the current in a circuit
- Describe the qualitative variation of resistance of light-dependent resistors (LDRs) with illumination and thermistors with temperature
- Know that lamps and LEDs can be used to indicate the presence of a current in a circuit
- Know and use the relationship between voltage, current and resistance: voltage = current x resistance, V = I x R
- Know that current is the rate of flow of charge
- Know and use the relationship between charge, current and time: charge = current x time, Q = I x t
- Know that electric current in solid metallic conductors is a flow of negatively charged electrons
- Understand why current is conserved at a junction in a circuit
- Know that the voltage across two components connected in parallel is the same
- Calculate the currents, voltages and resistances of two resistive components connected in a series circuit
- Know that voltage is the energy transferred per unit charge passed and that the volt is a joule per coulomb
- Know and use the relationship between energy transferred, charge and voltage: energy transferred = charge x voltage, E = Q x V
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Lesson Note
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Lesson Evaluation
Congratulations on completing the lesson on Energy And Voltage In Circuits. 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.
- What does electric current measure? A) The energy stored in a battery B) The rate of flow of charge C) The resistance of a wire D) The voltage across a component Answer: B
- A charge of 60 C passes through a lamp in 20 s. What is the current? A) 1200 A B) 80 A C) 3 A D) 0.33 A Answer: C
- Which I-V graph is a straight line through the origin? A) Filament lamp B) Diode C) Fixed resistor D) Thermistor Answer: C
- In a parallel circuit, what happens to the voltage across each branch? A) It is shared equally B) It is the same as the supply voltage C) It decreases along each branch D) It depends on the current Answer: B
- What happens to the resistance of a thermistor as temperature increases? A) It increases B) It decreases C) It stays the same D) It drops to zero Answer: B
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