S Current Electricity Flashcards
Current definition
The flow of electrons in a wire
What are substances that allow current to flow through them
Substances that allow current flow through them are called electrical conductors
Example tinfoil
What are substances that do not allow current/electricity to flow through them
Substances that do not allow current/ electricity to flow through them are called insulators
Example plastic
Lamp symbol
Circle with an x in it
Ammeter
Voltmeter
Ohm meter symbols
Circle with an A in it
Circle with a V in it
Circle with the ohm symbol in it
Resistor symbol
Empty Rectangle
What does an ammeter measure
Unit of current which is known as ampere or amps
What does a voltmeter measure
A voltmeter measures voltage or rather known as potential difference
What are bulbs in series
When bulbs are connected in series the same current Flows in both bulbs. if one bulb blows the other bulb will go out
What are bulbs in parallel
When bulbs are connected in parallel each bulb has an independent pathway for current to flow if one bulb blows the second can stay lit
What side of a battery is positive and what side of a battery is negative in a circuit symbol
The Long thin line is positive and the thick short line is negative
Why does a light bulb glow
What is resistance
The thin wire or filament in the bulb gets hot when a current flows through it.
the material from which the filament was made of has the tendency to resist movement of electrons
we say that the filament provided a resistance to the current
How many types of resistors is there
and what are they
What do they do?
There are two types of resistors fixed resistors and variable resistors
Fixed resistors have one value for resistance they are represented in a circuit diagram by a box.
Variable resistors are usually represented with the box with an arrow Crossing diagonally.
An example of a variable resistor is an LDR (light dependent resistor) or thermistor resistance of the thermistor decreases when it’s heated
What are the 4 symbols for resistors
Variable ressitor- rectangle with an arrow threw it
Thermistor- variable resistor with a straight line on the other end of the arrow
Fixed resistor- a rectangle
Light dependant resistor- fixed resistor ina circle with 2 arrows pointing at it
What is the relationship between voltage current and resistance
Voltage (V)
——-‐—————————————–
Resistance (ohm) × current(I)
What does a resistor do or change
A resistor changes the voltage in the circuit
What is Ohm’s law
For metallic conductor at constant temperature the current is proportional to the voltage
What is a diode
A diode is a device that allows current to flow through it in One Direction
What is a trick to know what way to place the diode in a circuit
Turn the triangle in the dial symbol into a p meaning positive.
The positive end of the battery or cell and the positive side of the diode have to be on the same side/meet.
What is a light emitting diode LED
An LED will only allow current to flow in One Direction
What is forward and reverse biased
Forward biased means the diode has been placed correctly and reverse bias means it has not
What is a light-dependent resistor LDR
Is a type of variable resistor that changes resistance dramatically in response to light
What is a thermistor
It is a device made of material that reduces its resistance significantly when the temperature of the device changes
Example temperature sensors, fire alarms, ovens and fridges
What is power
Power is the rate at which work is done
W
P= —
T
The greater the power of the appliance, the more energy it will convert from one form to another in one secondWhat is the connection with power voltage and current
How do you calculate electrical power
Voltage (V) × current (I)
