3Y: Electricity Flashcards
What is Current?
The flow of electrons in a wire.
What is an Insulator?
Insulators are substances that do not allow electricity to travel through them.
What is a Conductor?
Conductors are substances that allow electricity to travel through them.
What is an Ammeter?
An ammeter is a device that measures current.
What is Current measured in?
Current is measured in units called amps..
What is flowing in the wires?
- When electricity flows in a wire it is actually individual electrons that flow.
- These are the electrons that orbit the nucleus of the atom you studied in chemistry.
- Electrons are released from the negative side of the battery and pass from atom to atom of the metal in the wires. Eventually the electrons arrive back in the battery and re-enter the battery at the positive side.
- Such a flow of electrons is called electric current.
What causes a current to flow in the circuit?
- In order to get the electrons in a wire to move, the electrons must be given energy (pushed).
- This energy comes from the battery. You might like to think of a battery as a pump for electrons. This pushing power of a battery is measured in volts. Batteries are compared using their voltages.
- The voltage of a battery can be measured using a voltmeter
- The unit of voltage is the volt (V).
- Voltage is also referred to as potential difference as voltage is always measured between two points.
- It is important that you realise that potential difference is measured in volts with a voltmeter.
How can you measure resistance?
- Resistance can be measured with an ohmmeter. The unit of resistance is the ohm.
What are the 2 types of resistors?
- There are two types of resistor – fixed resistors and variable resistors.
- Fixed resistors have one value for resistance.
- Variable resistors are usually represented with a box with an arrow crossing diagonally. One type of variable resistor is the light-dependent resistor (LDR), whose resistance changes when light is shone on it. Another type of resistor is the thermistor. The resistance of the thermistor decreases when it is heated.
What is the relationship between voltage, current and resistance?
A scientist called Georg Ohm, a teacher from Germany, summarised the relationship between these three variables.
- Voltage = Current × Resistance
or in short;
- V = I × R
Unit of voltage = volt (V)
Unit of current (I) = amp (A)
Unit of resistance (R) = ohm (Ω)
What is Ohm’s Law?
- For a metallic conductor at constant temperature the current is proportional to the voltage.
This is one of the most basic laws of physics and it is important that you are able to state it!
What is a diode?
A diode is a device that allows current to flow through it in one direction only.
What is the power of an electrical appliance?
The power of an electrical appliance is a measure of the amount of electrical energy converted to other form each second.
How do you calculate Electrical Power?
power = voltage × current P = V × I
- P = power measured in watts (W)
- V = voltage measured in volts (V)
- I = current measured in amps (A)
What are the below labels?
What are the below labels?
What are the below labels?
What are the below labels?
What are the below labels?
What are the below labels?
