Electricity and energy Flashcards
Why do conductors conduct electricity?
The conductor allows the electrons to move freely (for example, a conductive material is copper)
What is direct current?
Direct current is when the electrons always flow around the circuit in the same direction, form negative to positive.
What is alternating current?
Alternating current is when the charges are continuously reversing, moving backwards and forwards many times per second.
What is an electric current?
A region of space where charges experience an electrical force.
What is the frequency of A.C current in the UK?
50 Hz
What is 1 volt equal to?
1 Joule per Coulomb
What is current?
Current is the flow of negative charges called electrons in a circuit.
What is voltage?
The measure of electrical energy given to each coulomb in a circuit.
At what voltage does a NPN transistor switch on?
When the voltage is greater than 0.7v
At what voltage does a MOSFET switch on?
When the voltage is greater than 2v
What is pressure?
The force applied per unit of area
What is the UK mains supply
230V
What are the two different transistors?
NPN transistor and MOSFET transistor
How does an NPN transistor work?
By applying a voltage between the base and emitter, the transistor can be made to conduct through the emitter and collector. The voltage required to switch on the transistor is 0.7V or above. Potential divider circuits can often be used to achieve this in a variety of situations.
What is the unit of pressure?
Pascal (Pa)
Boyle’s law
the pressure of a fixed mass of gas at constant temperature is inversely proportional to the volume.
Gay-Lussacs’ law
the pressure of a fixed mass of gas at constant volume is directly proportional to the temperature in Kelvin.
Charle’s law
the volume of a fixed mass of gas at constant pressure is directly proportional to the temperature in Kelvin.
Specific latent heat of fusion
the energy required to change 1 kg of a substance from a solid to a liquid without changing the temperature
Temperature
a measure of the mean kinetic energy (speed) of the particles in a substance
Absolute zero
-273 degree Celsius
What is resistance
Resistance is the measure of the current restricted. Resistance makes the current smaller.
3A fuse
= under 720 W
13A fuse
= over 720 W
what is electrical power
Electrical Power is the energy transferred in a period of time in a circuit.
when does a charged particle experience a force?
a charged particle experiences a force in an electric field
Switch
A switch allows you to complete or break a circuit
Lamp
A lamp lights when current flows through it, converting electric energy into light energy
Thermistor
The resistance of a thermistor will decrease as the temperature increases
Light dependant resistor (LDR)
Can be used to control a circuit. The resistance goes down as the light increases
Ammeter
Must be placed in series to measure the current flowing in a circuit
Light emitting diode (LED)
Emits light when a current flows but only allows current to flow in one direction. Requires less energy than a lamp
Cell
Supplies electrical energy to a circuit, the longer line shows the positive side
Battery
A battery of cells means 2 or more cells
DC supply
Supplies electrical energy to a circuit in the form of a direct current
Ohmmeter
Measures resistance - must be placed in parallel with the components which are to be measured
Voltmeter
Must be placed in parallel to measure the difference in electrical potential between two points
AC supply
Supplies electrical energy to a circuit in the form of an alternating current
Fuse
A fuse is a safety device - the metal core will melt when too much current is flowing in the circuit
Diode
Only allows current to flow in one direction
Capacitor
Used to store electrical charge, can be used to create a simple timing circuit, or in the flash of a camera
Photovoltaic cell
Converts light energy into electrical energy, can be used as the power source in a circuit. More light will mean a greater P.D around the circuit
Loudspeaker
Converts electrical energy into sound energy
Microphone
Converts sound energy into electrical energy
Motor
Converts electrical into kinetic energy by turning
Variable resistor
A resistor, the resistance of which can be varied in the circuit, could be used for a dimmer switch
Resistor
A resistor restricts the flow of current, this may be to protect other compounds
