Edexcel iGCSE Physics - 2.1 Electrical Units- Study Notes- New Syllabus
Edexcel iGCSE Physics -2.1 Electrical Units- Study Notes- New syllabus
Edexcel iGCSE Physics -2.1 Electrical Units- Study Notes -Edexcel iGCSE Physics – per latest Syllabus.
Key Concepts:
2.1 use the following units: ampere (A), coulomb (C), joule (J), ohm (Ω), second (s), volt (V) and watt (W)
Electrical Quantities and Their Units
Electrical quantities describe how electric charge flows, how energy is transferred, and how electrical devices operate. Each quantity has a specific SI unit that must be used correctly in calculations.
Electrical Units Used in Physics
- Current → ampere (A)
- Charge → coulomb (C)
- Energy → joule (J)
- Resistance → ohm (Ω)
- Time → second (s)
- Potential difference → volt (V)
- Power → watt (W)
Electric Current (A)
Electric current is the rate of flow of charge.
\( \mathrm{current = \dfrac{charge}{time}} \)
\( \mathrm{I = \dfrac{Q}{t}} \)
- Current is measured in amperes (A).
- 1 A means 1 coulomb of charge flows each second.
Electric Charge (C)
Electric charge is the amount of electricity that flows.
\( \mathrm{charge = current \times time} \)
\( \mathrm{Q = It} \)
- Charge is measured in coulombs (C).
Potential Difference (V)
Potential difference is the energy transferred per unit charge.
\( \mathrm{potential\ difference = \dfrac{energy}{charge}} \)
\( \mathrm{V = \dfrac{E}{Q}} \)
- Measured in volts (V).
Electrical Energy (J)
Electrical energy is the energy transferred by an electric current.
\( \mathrm{energy = charge \times potential\ difference} \)
\( \mathrm{E = QV} \)
- Measured in joules (J).
Resistance (Ω)
Resistance is the opposition to the flow of current.
\( \mathrm{resistance = \dfrac{potential\ difference}{current}} \)
\( \mathrm{R = \dfrac{V}{I}} \)
- Measured in ohms (Ω).
Electrical Power (W)
Electrical power is the rate of energy transfer.
\( \mathrm{power = energy \div time} \)
\( \mathrm{P = \dfrac{E}{t}} \)
Common alternative form:
\( \mathrm{P = VI} \)
- Power is measured in watts (W).
Key Idea
- Each electrical quantity has a specific SI unit.
- Formulas link these quantities together.
- Correct units are essential in calculations.
Important Points to Remember
- Always convert values to SI units.
- Use the correct equation for the quantity required.
- Include units in final answers.
Example
A current of \( \mathrm{2\ A} \) flows for \( \mathrm{5\ s} \). Calculate the charge transferred.
▶️ Answer / Explanation
Use: \( \mathrm{Q = It} \)
\( \mathrm{Q = 2 \times 5} \)
\( \mathrm{Q = 10\ C} \)
Example
An appliance operates at \( \mathrm{230\ V} \) and draws a current of \( \mathrm{4\ A} \). Calculate the power of the appliance.
▶️ Answer / Explanation
Use: \( \mathrm{P = VI} \)
\( \mathrm{P = 230 \times 4} \)
\( \mathrm{P = 920\ W} \)