Current
- Rate at which charge flows through a surface I=Q/t, where I=current;Q=charge; t= time
- I is measured in Amperes (A) = 1C/s
- Analogy: rate at which blood flows through a vein or artery
- Current direction convention is to give the current flow the same direction as the flow of positive charges Therefore, current flows from the positive to the negative terminal of a battery
Voltage
- The battery provides the emf in the circuit
- Emf = electromotive force; another term for potential difference or voltage; measured in Volts (V)
- Analogy: the heart provides the flow of blood just as the battery provides the flow rate of charges (current) in the circuit
- The heart/artery/vein system is a closed system just like an electric circuit
Resistance
- Provides a deterrent to the flow of current in the circuit
- Resistors are used to reduce the amount of current
- At a constant voltage, R and I are inversely related
- Analogy: Plaque build-up in the artery inhibits blood flow
- Resistors can be fixed or variable in a circuit
- Examples of appliances with variable resistors: toaster, iron, hairdryer. Resistance occurs because the electrons are restricted by the walls of the wires
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