Electricity Flashcards
What is an ion?
A charged atom
How does charging by friction work?
When you rub an insulator, electrons are transferred from one of the materials to the other causing them to become charged.
What type of force do two charged objects exert on each other?
non-contact force
Why do two charged objects exert a non-contact force?
A charged object has an electric field around itself.
What does each line of force represent?
the path that a small positive charge would follow because of the electric field.
If the sphere was negatively charged, what way would the lines of force point?
towards the centre of the sphere.
How does sparking occur?
When two oppositely charged objects are in close proximity and the electric field around them becomes too strong. This causes some of the electrons to be pulled out of air molecules which then hit other air molecules creating a sudden flow of electrons.
Complete the sentences: Like charges _______. Unlike charges______.
repel, attract
What is electric current?
The flow of charge/ electrons.
What is used to measure current?
ammeter
What is a battery?
two or more cells
What is electric charge measured in?
coulombs
What is the equation linking charge, time and current?
charge = current x time
What is potential difference?
The energy transferred by each coulomb of charge that passes a point.
What is the equation linking energy transferred, charge and potential difference?
potential difference = energy transferred / time
What is resistance?
when atoms resist the passage of electrons through a circuit
What is the equation linking potential difference, resistance and current?
V = IR
What is Ohm’s law?
The current through a resistor at constant temperature is directly proportional to the potential difference across the resistor.
What is an ohmic conductor?
Something that has a constant resistance whilst current changes.
Complete the sentence : The greater the resistance, the _______ steep the line.
less
What does reversing the potential diff across a resistor do to the current?
reverses it
How can you investigate how the length of a wire affects the resistance? RP
- Set up a series circuit with a cell, switch, ammeter, wire and voltmeter added in parallel.
- To add the wire tape it to a metre ruler and add crocodile clips 10cm apart.
- Calculate the resistance of the circuit using R = V/I
- Repeat by increasing the distance of the crocodile clips by 10cm each time.
- Record the results
What is a zero error?
A reading on a measuring instrument when the value should be zero.
If the temperature of the wire increases, what will happen to the resistance?
It will increase
What can you do to reduce the effects of heating when investigating the length of wire on resistance?
- Low potential difference
- Turn off the current when taking a reading
Draw a current-potential difference graph for a filament lamp.
Curved
Draw the current-potential difference graph for a diode.
Straight line across x axis then increase in current.
What direction does current flow through a diode?
One direction, called the forward direction
What way does the line curve in the forward direction of a diode?
towards the y axis
What is a diode?
a non-ohmic conductor