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Electric Current
Current (I) is the flow of charge in a circuit.
Current Measurement
Measured in amperes (A) using an ammeter, which is placed in series.
Current Formula
Q = charge (Coulombs, C), I = current (Amperes, A), t = time (seconds, s)
Potential Difference (Voltage)
Potential difference (V) is the energy transferred per unit charge.
Voltage Measurement
Measured in volts (V) using a voltmeter, which is placed in parallel.
Voltage Formula
V = voltage (Volts, V), E = energy transferred (Joules, J), Q = charge (Coulombs, C)
Resistance
Resistance (R) opposes current flow. Higher resistance = lower current.
Resistance Measurement
Measured in ohms (Ω).
Ohm's Law
V = potential difference (V), I = current (A), R = resistance (Ω)
Resistor
Straight line through origin; Constant resistance.
Filament Lamp
Curve; Resistance increases as temperature increases.
Diode
Current flows in one direction; High resistance in reverse direction.
LDR
More light = lower resistance; Used in automatic lights.
Thermistor
Higher temperature = lower resistance; Used in thermostats.
Aim of Resistance Investigation
To investigate how the resistance of a wire changes with length.
Required Apparatus
Power supply, Ammeter, Voltmeter, Thin nichrome wire, Meter ruler, Connecting wires, Crocodile clips.
Resistance Calculation Method
Calculate resistance (R) using Ohm's Law.
Graph Relationship
The graph should show a directly proportional relationship: longer wire = higher resistance.
Reason for Resistance Increase
Longer wires have more collisions between electrons and atoms, increasing resistance.
Independent Variable
Wire length.
Dependent Variable
Resistance.
Control Variables
Wire type, temperature.
