Physics: Electricity
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39 Terms
How can an insulator become electrically charged?
By friction causing a transfer of electrons.
What causes an object to become positively charged?
Loss of electrons.
What causes an object to become negatively charged?
Gain of electrons.
What happens when two like charges are brought together?
They repel.
What happens when two unlike charges are brought together?
They attract.
Why is earthing used?
To safely remove excess charge and reduce electrostatic hazards.
Give one application of electrostatics.
Electrostatic paint spraying or photocopiers.
Give one hazard associated with electrostatics.
Sparks causing fires or explosions.
What is the circuit symbol for a cell?
A single long and short parallel line.
What is the circuit symbol for a battery?
Two or more cells connected together.
What is the circuit symbol for a resistor?
A rectangle.
What is the circuit symbol for a variable resistor?
A resistor with a diagonal arrow.
What is the circuit symbol for an ammeter?
A circle containing A.
What is the circuit symbol for a voltmeter?
A circle containing V.
What is the circuit symbol for a switch?
A break in the circuit with a movable contact.
What is the circuit symbol for a diode?
A triangle-free diode symbol allowing one-way current flow.
What is direct current (dc)?
Current flowing in one direction only.
What is alternating current (ac)?
Current that continually changes direction.
What is a conductor?
A material that allows charge to flow easily.
What is an insulator?
A material that resists the flow of charge.
State the equation relating current, charge and time.
I = Q/t.
What instrument measures current?
An ammeter.
How should an ammeter be connected?
In series.
What instrument measures potential difference?
A voltmeter.
How should a voltmeter be connected?
In parallel.
State the equation relating resistance, voltage and current.
R = V/I.
How does the V-I graph of a fixed resistor behave?
It is a straight line through the origin.
How does the V-I graph of a filament lamp behave?
It curves because resistance increases as temperature increases.
How does the resistance of an NTC thermistor change as temperature increases?
It decreases.
How does the resistance of an LDR change as light intensity increases?
It decreases.
What is the function of an ideal diode?
It allows current to flow in one direction only.
What is the current rule for a series circuit?
The current is the same everywhere.
What is the voltage rule for a series circuit?
The voltages add to the supply voltage.
What is the voltage rule for a parallel circuit?
The potential difference is the same across each branch.
How is the total resistance of resistors in series found?
Add the resistances.
How does the total resistance of parallel resistors compare with the individual resistances?
It is less than the smallest individual resistance.
State the equation relating potential difference, energy and charge.
V = E/Q.
State the electrical power equations.
P = IV = I²R.
State the equation for electrical energy transferred.
E = VIt.