Glossary
Current (I)
Current is the rate of flow of electric charge through a conductor, measured in amperes (A).
Example:
When you turn on a powerful appliance, a large current flows from the wall outlet, indicating many electrons are moving through the circuit each second.
Energy Dissipation (as thermal energy)
Energy dissipation refers to the conversion of electrical energy into heat, primarily occurring in resistors as current flows through them due to their opposition to charge movement.
Example:
When a laptop charger gets warm during use, it's experiencing energy dissipation as thermal energy, a common byproduct of electrical resistance.
I-V Graph (Current-Voltage Graph)
An I-V graph plots current (I) as a function of voltage (V) for a circuit element, where the slope (or inverse slope) can be used to determine the element's resistance.
Example:
By plotting the measured current against the applied voltage, a student can create an I-V graph to visually confirm if a material is ohmic and calculate its resistance from the graph's slope.
Ohm's Law
Ohm's Law describes the fundamental relationship between voltage (V), current (I), and resistance (R) in a circuit, expressed by the equation V = IR.
Example:
If a light bulb connected to a 6V battery draws 0.5A of current, you can use Ohm's Law to calculate its resistance as 12Ω.
Ohmic Materials
Ohmic materials are substances whose resistance remains constant regardless of the current flowing through them, resulting in a linear current-voltage (I-V) graph.
Example:
Most common metal wires behave as ohmic materials under normal conditions, maintaining a consistent resistance as voltage changes.
Resistance (R)
Resistance is the opposition to the flow of electric current, measured in ohms (Ω), and depends on a material's resistivity, length, and cross-sectional area.
Example:
A long, thin wire has higher resistance than a short, thick wire of the same material, making it harder for current to pass through.
Resistivity (ρ)
Resistivity is an intrinsic material property that quantifies how strongly a material opposes the flow of electric current, measured in ohm-meters (Ω⋅m).
Example:
Silver has a very low resistivity, making it an excellent conductor, while rubber has high resistivity, making it an effective insulator.
Resistors
Resistors are circuit components specifically designed to introduce a controlled amount of resistance into a circuit, converting electrical energy into thermal energy.
Example:
The small cylindrical components with colored bands on a circuit board are resistors, used to limit current or divide voltage within the circuit.
Voltage (V)
Voltage is the electrical potential difference across a component in a circuit, representing the 'push' or energy per unit charge, measured in volts (V).
Example:
A standard AA battery provides 1.5V of voltage, which is the electrical 'pressure' that drives current through a connected device.