Electricity and Electrical Circuits
Physics Study Notes | 4 November 2026
1. Electricity
Electricity is associated with electric charge and its movement. In many everyday circuits, moving electrons in a conductor
create electric current.
2. Electric Charge
There are positive and negative charges. Like charges repel; opposite charges attract. Charge is measured in coulombs (C).
3. Conductors and Insulators
Conductors such as copper allow charge to move easily. Insulators such as rubber and glass resist charge movement.
4. Current
Electric current is the rate of flow of charge. It is measured in amperes (A). Formula: I = Q ÷ t.
5. Voltage and Resistance
Voltage is electrical potential difference, measured in volts (V). Resistance opposes current and is measured in ohms (Ω).
6. Ohm's Law
For many components under constant conditions: V = I × R. Rearranged: I = V ÷ R and R = V ÷ I.
7. Series Circuits
A series circuit has one path. Current is the same through all components. Total resistance is Rtotal = R1 + R2 + R3.
8. Parallel Circuits
A parallel circuit has multiple branches. Voltage is the same across each branch, while current divides between branches.
9. Power and Energy
Electrical power is the rate of energy transfer, measured in watts (W). P = V × I. Energy: E = P × t. Household energy is often
measured in kilowatt-hours (kWh).
10. Circuit Components
A cell or battery supplies energy; wires provide a path; a switch opens or closes a circuit; a resistor limits current; a lamp
converts electrical energy into light and heat.
11. Electrical Safety
Never experiment with mains electricity or damaged equipment. Use only purpose-built low-voltage learning kits with adult or
teacher supervision. Keep devices away from water and report damaged cables.
12. Key Terms
Current: Rate of charge flow. Voltage: Potential difference. Resistance: Opposition to current. Conductor: Allows charge
to move easily. Insulator: Resists charge movement. Circuit: A complete path for current.
13. Short Q&A;
Q1. What is current? Rate of flow of electric charge.
Q2. Unit of current? Ampere.
Q3. State Ohm's law. V = I × R.
Q4. Give one conductor. Copper.
Q5. How does a parallel circuit differ from a series circuit? It has multiple branches instead of one path.
14. MCQs
Physics Study Notes | 4 November 2026
1. Electricity
Electricity is associated with electric charge and its movement. In many everyday circuits, moving electrons in a conductor
create electric current.
2. Electric Charge
There are positive and negative charges. Like charges repel; opposite charges attract. Charge is measured in coulombs (C).
3. Conductors and Insulators
Conductors such as copper allow charge to move easily. Insulators such as rubber and glass resist charge movement.
4. Current
Electric current is the rate of flow of charge. It is measured in amperes (A). Formula: I = Q ÷ t.
5. Voltage and Resistance
Voltage is electrical potential difference, measured in volts (V). Resistance opposes current and is measured in ohms (Ω).
6. Ohm's Law
For many components under constant conditions: V = I × R. Rearranged: I = V ÷ R and R = V ÷ I.
7. Series Circuits
A series circuit has one path. Current is the same through all components. Total resistance is Rtotal = R1 + R2 + R3.
8. Parallel Circuits
A parallel circuit has multiple branches. Voltage is the same across each branch, while current divides between branches.
9. Power and Energy
Electrical power is the rate of energy transfer, measured in watts (W). P = V × I. Energy: E = P × t. Household energy is often
measured in kilowatt-hours (kWh).
10. Circuit Components
A cell or battery supplies energy; wires provide a path; a switch opens or closes a circuit; a resistor limits current; a lamp
converts electrical energy into light and heat.
11. Electrical Safety
Never experiment with mains electricity or damaged equipment. Use only purpose-built low-voltage learning kits with adult or
teacher supervision. Keep devices away from water and report damaged cables.
12. Key Terms
Current: Rate of charge flow. Voltage: Potential difference. Resistance: Opposition to current. Conductor: Allows charge
to move easily. Insulator: Resists charge movement. Circuit: A complete path for current.
13. Short Q&A;
Q1. What is current? Rate of flow of electric charge.
Q2. Unit of current? Ampere.
Q3. State Ohm's law. V = I × R.
Q4. Give one conductor. Copper.
Q5. How does a parallel circuit differ from a series circuit? It has multiple branches instead of one path.
14. MCQs
