Chapter 10 D.C. Circuits Flashcards
Switch:
Turn the circuit on (closed), or off (open)
Fixed resistor:
A resistor limits the flow of current. A fixed resistor has a resistance it cannot change
Variable resistor:
A resistor with a slider that can be used to change its resistance. Used often in dimmer switches and volume controls
Thermistor:
The resistance of a thermistor depends on its temperature. As its temperature increases, its resistance decreases and vice versa
Light-dependent resistor (LDR):
The resistance of an LDR depends on the light intensity. As the light intensity increases, its resistance decreases and vice versa
Diode:
A diode allows current to flow in one direction only. They are used to convert AC to DC current
Light-emitting diode (LED):
This is equivalent to a diode and emits light when a current passes through it. These are used for aviation lighting and displays (TVs, road signs)
Ammeter:
Used to measure the current in a circuit. Connected in series with other component
Voltmeter:
Use to measure the potential difference of an electrical component. Connected in parallel with component
Electromotive Force
- When charge passes through a power supply such as a battery, it gains electrical energy
- The electromotive force (e.m.f) is the amount of chemical energy converted to electrical energy per coulomb of charge (C) when charge passes through a power supply
- e.m.f is measured in Volts (V)
e.m.f is also
- the potential difference across the cell when no current is flowing e.m.f can be measured by connecting a high-resistance voltmeter around the terminals of the cell in an open circuit
potential difference
- Potential difference describes the loss of energy from charges; ie. when electrical energy is transferred to other forms of energy in a component
-e.m.f. describes the transfer of energy
- from the power supply to electrical charges within the circuit
Internal Resistance
- All power supplies have some resistance between their terminals
- This is called internal resistance (r)
internal resistance causes the
- charge circulating to dissipate some electrical energy from the power supply itself
- This is why the cell becomes warm after a period of time
e.m.f equation