Concepts and Definitions
Define electric current and state its SI unit
Electric current is the flow of electric charge through a conductor.
Its SI unit is the ampere (A).
A circuit has a current of 2 A flowing through a resistor of 5 Ω. Calculate the potential difference across the resistor.
V=IR
=2×5
=10 V
In a series circuit, what happens to the current when more resistors are added
The total resistance increases, so the current decreases.
Write the formula for electrical power and define each variable
P=VI
P = Power (W)
V = Voltage (V)
I = Current (A)
What is the difference between a conductor and an insulator
A conductor allows the flow of electric current
An insulator resists the flow of electric current
A 12 V battery supplies power to a 3 Ω resistor. Calculate the current in the circuit
(/) division
I=V/R
=12/3
=4 A
In a parallel circuit, why is the total resistance always less than the smallest resistor
In parallel circuits, adding more paths for current reduces overall resistance.
Calculate the power dissipated in a resistor with a resistance of 20 Ω and a current of 3 A
P=I^2xR
=3^2×20
=9×20
=180W
Explain Ohm’s Law in words and provide its formula
Ohm's Law states that the current through a conductor is directly proportional to the voltage across it, provided the temperature remains constant.
Formula: V=IR
Calculate the total resistance in a series circuit with three resistors of 4 Ω, 6 Ω, and 8 Ω.
Rtotal=R1+R2+R3
=4+6+8
=18Ω.
Explain the difference between voltage distribution in series and parallel circuits
In series circuits, the voltage is divided across components. In parallel circuits, the voltage is the same across all branches
How much energy is consumed by a 100 W light bulb operating for 5 hours
Energy = Power × Time
= 100×5
=500 Wh
=0.5 kWh
What is meant by potential difference in a circuit
Potential difference is the energy transferred per unit charge between two points in a circuit. It is measured in volts (V)
If a parallel circuit has two resistors (10 Ω and 15 Ω), calculate the total resistance
1/Rtotal=1/10+1/15
1/Rtotal=3/30+2/30
1/Rtotal=5/30
Rtotal=6 Ω
What happens to the total current in a parallel circuit if an additional branch is added
The total current increases because the overall resistance decreases
A device operates at 240 V and uses 3 kW of power. Calculate the current through the device
I=P/V
=3000/240
=12.5 A
What is resistance
Resistance is the opposition to the flow of current in a conductor.
A 24 V battery is connected to a circuit with a total resistance of 8 Ω. Calculate the current.
I=V/R
=24/8
=3 A
What is the advantage of connecting appliances in parallel in household circuits
In parallel, each appliance receives the same voltage, and a failure in one appliance does not affect the others
What is the cost of using a 1.5 kW heater for 4 hours if electricity costs R2 per kWh
Energy = 1.5×4
=6 kWh
Cost = 6×2
=R12