Electric Current
Electromotive Force and Potential Difference
Resistance and Resistivity
IGCSE Physics: Current Electricity
BeeSmart Education
April 13, 2025
BeeSmart Education
IGCSE Physics: Current Electricity
Electric Current
Electromotive Force and Potential Difference
Resistance and Resistivity
What is Electric Current?
Definition: Electric current (I ) is the rate of flow of electric
charge in a circuit. It is measured in Amperes (A).
Formula:
I =
Q
t
where:
I = Current (A)
Q = Charge (Coulombs)
t = Time (s)
Key Points:
Electrons carry charge in metals.
Conventional current flows from positive to negative.
BeeSmart Education
IGCSE Physics: Current Electricity
Electric Current
Electromotive Force and Potential Difference
Resistance and Resistivity
Illustration of Electric Current
I
+
−
Conventional Current Direction: Current flows from the
positive to the negative terminal.
BeeSmart Education
IGCSE Physics: Current Electricity
Electric Current
Electromotive Force and Potential Difference
Resistance and Resistivity
Electromotive Force (EMF)
Definition: EMF (E) is the total energy supplied per unit charge
by the source.
Formula:
W
E=
Q
where:
E = EMF (Volts)
W = Work Done (Joules)
Q = Charge (Coulombs)
BeeSmart Education
IGCSE Physics: Current Electricity
Electric Current
Electromotive Force and Potential Difference
Resistance and Resistivity
Potential Difference (Voltage)
Definition: Potential difference (V ) is the energy used per unit
charge to move between two points in a circuit.
Formula:
W
V =
Q
It is measured in **Volts (V)**.
BeeSmart Education
IGCSE Physics: Current Electricity
Electric Current
Electromotive Force and Potential Difference
Resistance and Resistivity
EMF vs. Potential Difference
Electromotive Force (EMF)
Total energy supplied
Source of electrical energy
Measured across power supply
BeeSmart Education
Potential Difference (Voltage)
Energy used between two points
Work done in a circuit
Measured across components
IGCSE Physics: Current Electricity
Electric Current
Electromotive Force and Potential Difference
Resistance and Resistivity
Resistance
Definition: Resistance (R) opposes the flow of current in a circuit.
Formula:
V
R=
I
where:
R = Resistance (Ω)
V = Voltage (V)
I = Current (A)
BeeSmart Education
IGCSE Physics: Current Electricity
Electric Current
Electromotive Force and Potential Difference
Resistance and Resistivity
Resistivity
Definition: Resistivity (ρ) is a material property that affects its
resistance.
Formula:
L
R=ρ
A
where:
R = Resistance (Ω)
ρ = Resistivity (Ω · m)
L = Length of conductor (m)
A = Cross-sectional area (m2 )
BeeSmart Education
IGCSE Physics: Current Electricity
Electric Current
Electromotive Force and Potential Difference
Resistance and Resistivity
Factors Affecting Resistance
Length L: Longer wires have higher resistance.
Area A: Thicker wires have lower resistance.
Material ρ: Copper has low resistivity, rubber has high
resistivity.
Temperature: Higher temperature increases resistance in
metals.
BeeSmart Education
IGCSE Physics: Current Electricity
Electric Current
Electromotive Force and Potential Difference
Resistance and Resistivity
Illustration: Resistance in a Wire
I
R
BeeSmart Education
I
IGCSE Physics: Current Electricity