Electricity Flashcards
What do the same type of charges do?
Repel
What do opposite charges do?
Attract
How many types of electric charges are there?
2 A positive or a negative charge
What is an electrostatic charge?
This occurs when a charge builds up on the surface of an object and cannot move This happens most often when you rub certain types of insulators together. You remove or add a small amount of electrons (negative charge) from one to the other. This leaves one slightly positively charge and one slightly negatively charged.
What is current?
An electric current is a flow of charge In an electric circuit negative electrons flow
What is potential difference?
The difference in electrical pressure between two points in a circuit It shows how must energy has been transferred (work done) for each coulomb of charge (the unit we measure charge in) It is measured in Volts (V)
What is charge measured in?
Coulomb (C)
What is resistance?
Something which restricts the flow of current in a circuit. The more it restricts it the higher the resistance.
How are current, potential difference and resistance related?
Voltage = Current x Potential difference V = I x R
What is an LED?
Light Emitting Diode Produces light when a current flows through it They have a high efficiency and last a long time They use a much smaller current compared to other forms of lighting
What is a diode
A component which lets the current flow through it in only one direction.
What happens to the resistance of a filament bulb as the temperature increases?
As temperature increases the resistance will also increase This is due to the ions in the metals, which begin to vibrate more as temperature increases (remember kinetic theory). These means the electrons start to know into more and more of them decreasing their overall flow.
Light dependent resistor
Special type of resistor. Its resistance changes as the intensity of the light falling on it changes. When the light levels are low, resistance is high When light levels are high, resistance is much lower
What is a thermistor?
Special resistor whose resistance changes as the temperature changes High temperature, low resistance Low temperature, high resistance
What is direct current (DC)
A current which remains constant all the time Examples are current from a battery
What is alternating current (AC)?
Here the current is constantly changing and varies between a maximum positive and negative value The current in the mains is AC Currents from any generator will produce an AC supply
What is the voltage and frequency of the alternating current in the mains?
230V a.c. and 50Hz
What does this electrical symbol stand for?
Voltmeter
measures potential different between two points in the circuit
Must be placed in parallel to the component(s) being measured
What does this electrical symbol stand for?
Variable resistor
What does this electrical symbol stand for?
Thermistor
As temperature increases the resistance decreases
What does this electrical symbol stand for?
Switch
What does this electrical symbol stand for?
Resistor
What does this electrical symbol stand for?
LED
Light Emitting Diode
What does this electrical symbol stand for?
LDR
Light Dependent Resistor
As the light level increases the resistance drops
