Circuits Flashcards
What is a cell
A cell is necessary to push electrons around a complete circuit
What is a battery
A battery consists of two or more cells
What is a switch
A Switch enables the current in a circuit to be switched on or off
What is an indicator
An indicator e.g. a bulb, is designed to emit light as a signal when current passes through it
What is a diode
A diode allows current to flow through it in one direction only
What is a light emitting diode
A light-emitting diode emits light when a current passes through it
What is a fixed resistor
A fixed resistor limits the current in a circuit
What is a variable resistor
A variable resistor allows the current to be varied
What is a fuse
A fuse is designed to melt and therefore ‘break; the circuit if the current through it is greater than a certain amount
What is a voltmeter
A voltmeter is used to measure potential difference
What is electricity
Electricity is the flow of charge around a circuit
What is the charge carried by
The charge is carried by electrons
In which direction does current flow
Current flows from the positive side of the cell to the negative side of the cell
In which direction do the electrons flow and why?
Electrons are attracted to the positive side of the cell so therefore flow from the positive side of the cell to the negative side of the cell
Define current
Current is the rate of flow of charge (how much charge is flowing per second)
A current of 2 amps flows for 10 seconds
Calculate the charge flowing through the circuit and the number of electrons flowing through the circuit
Q = I x t
Q = 2 x 10
Q = 20C
Number of electrons = 20/1.6 x10^-19 = 1.25 x10^20 electrons
Number of electrons = total charge / charge of one electron
What is voltage
Voltage provides the force that makes the electrons flow, it also provides energy to the electrons
What does an increase in voltage mean
More voltage means more electrons are flowing giving a greater current and more energy goes into the circuit
What is voltage in terms of energy and coloumbs
The voltage is the energy carried by one coulomb of charge
What is resistance
Resistance in a circuit is caused by the interaction of the electrons and the positive ions
Explain why the greater the resistance, the lower the current
When the electrons collide with the positive ions, the flow of electrons decreases, the flow of charge decreases and therefore the current decreases.
Therefore the greater the resistance, the lower the current.
Explain how resistance causes an increase in the temperature of the metal
When the electrons collide with the positive ions, they transfer kinetic energy to the positive ions.
The internal energy of the positive ions increases, causing an increase in the temperature of the metal
Draw the circuit diagram for investigating the relationship for current and voltage for a bulb (filament lamp)
Include
A variable power supply (a normal power supply with an arrow through it)
An ammeter
A filament lamp
Voltmeter connected to the filament lamp in parallel
State the method for investigating the relationship for current and voltage for a bulb (filament lamp)
Increase the voltage from the power supply and record the readings from the ammeter and voltmeter
Repeat each reading twice, and then calculate an average
Draw the graph for investigating the relationship for current and voltage for a bulb (filament lamp)
Current on y-axis
Voltage on x-axis
Curve
Explain why the current increases when the voltage increases
investigating the relationship for current and voltage for a bulb (filament lamp)
Voltage provides the force that makes electrons flow, it also provides energy to the electrons
Therefore more voltage means more electrons are flowing giving a greater current
Explain why the resistance of the bulb increases when the voltage increases
investigating the relationship for current and voltage for a bulb (filament lamp)
As voltage increases, the current increases, there are more collisions between the electrons and positive ions so positive ions gain more energy meaning they vibrate more.
This causes the temperature increases and therefore resistance
Explain why the graph curves - for investigating the relationship for current and voltage for a bulb (filament lamp)
Because the resistance increases, the voltage increases at a greater rate than the current, therefore the graph curves.
