Electric Current And Circuits Flashcards
What is a cell and learn symbol?
What is the battery and learn symbol?
A cell pushes electrons around a circuit.
A battery consists of 2 or more cells.
+ symbol indicates the positive terminal of the cell
- symbol indicates the negative terminal of the cell
What is a switch and learn its symbol?
A switch enables current in the circuit to be switched on and/or off
What is a lamp or bulb and it’s symbol?
An indicator such as a bulb designed to emit light when a current passes through it
What is a diode and it’s symbol?
A diode allows current through in one direction only
What is an LED and it’s symbol?
Light emitting diode
Emits light when a current passes through it
What is an ammeter and it’s symbol?
An ammeter measures electric current in amps
What is a resistor and it’s symbol?
A fixed resistor limits a current in a circuit
What is a variable resistor and it’s symbol?
Allows current to be varied
What is a fuse and it’s symbol?
A fuse is designed to melt and therefore break the circuit if the current going through it is greater than a certain amount
What is a voltmeter and it’s symbol?
A voltmeter is used to measure potential difference in volts or voltage
What is a thermistor and a LDR and learn symbols?
Thermistor = a temperature-dependent resistor and its resistance decreases if its temperature increases (and increases if its temperature decreases)
LDR - a light-dependent resistor and its resistance decreases if its light intensity increases (and increases if its light intensity decreases)
What is electric current?
A flow of electric charge
The size of current is rate of flow of electric charge
How do we measure current - equation?
Current (A)= charge(C)➗time(s)
I=Q➗T
If a charge of 6C flows through a bulb in 2 seconds what current flows?
I= Q/T
I=6/2
I=3A
Current is measured in amps
A current of 3A flows through a bulb for 10 seconds.
How much charge has passed through in this time?
I=Q/T 3=Q/10 Q=3x10 Q=30C Charge is measured in coulombs
A current of 6A is flowing.
How long does it take for 60C to flow through the point?
T=Q/I
T=60/6
T=10 seconds
Time is measured in seconds
How does current move?
Electrons move from the negative terminal of a cell to the positive terminal of a cell
What was conventional current?
Conventional current was when current flowed from the positive terminal to the negative terminal of a cell
How is the current through a component measured by?
It is measured by an ammeter alongside the component
What is Ohms law?
The current through a resistor at constant temperature is directly proportional to the potential difference across the resistor
Explain current in s series circuit
In a series circuit the same current passes through each component
Explain potential difference in a series circuit
In a series circuit the total potential difference of the power supply is shared between the components
What happens if you use more than one cell in a circuit
The total potential difference of cells in series is the sum of the potential difference of each cell
What is the resistance rule for components in series
The total resistance of 2 or more components in series is equal to the sum of the resistance of each component
Rt=R1+R2
Why does the resistance of several resistors in series increase if an additional resistor is connected
Adding more resistors in series increases the total resistance because the current through the resistors is reduced and the total potential difference across them is unchanged
How is current measured in parallel circuits
The total current through the whole circuit is the sum of the currents through the separate branches
Explain potential difference in a parallel circuit
For components in parallel the potential difference across each component is the same
How does current change in parallel circuits each with a different resistor
The bigger the resistance of the component the smaller the current through it
I= V/R
What is the rule for resistors in parallel
The total resistance of 2 or more components in parallel is less then the resistance of the resistor with the least resistance
The total potential difference is unchanged
