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41 Cards in this Set
- Front
- Back
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What causes static electricity? |
Friction between two insulators |
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What is static electricity? |
When charges are not free to move |
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How does friction between two insulators generate static electricity? |
Electrons are transferred from one object onto the next |
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If I use the same cloth on two rods made of the same material, which will repel and which will attract? |
The two rods will repel because they have the same charge. The cloth will attract the rods because they have opposite charges |
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Why do electric shocks occur when you touch a metal door handle? |
The metal is a conductor which allows the charges to flow causing a current which you feel as a shock. |
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If you've rubbed your hair with a balloon, why does it stand on end? |
All the hairs have the same charge so they repel each other. |
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What is an electric current? |
A flow of charges around a circuit |
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What is a conductor? |
Something that allows charges to flow through it |
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What does current depend on? |
voltage and resistance |
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What effect does increasing voltage have on current? |
It increases |
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What effect does increasing resistance have on current? |
It decreases. |
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What is power? |
The rate of energy transfer |
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What is work? |
The energy transferred (same as power) |
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What is the formula for power? |
voltage x current |
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What are the symbols for: Switch, Battery/Cell, lamp, voltmeter, ammeter, resistor, variable resistor and motor |
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What does a voltmeter measure? |
The potential difference between two points (the amount of energy transferred to a component) |
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What does the slope of a voltage-current graph show? |
The resistance |
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Explain the graph |
The higher the resistance, the steeper the slope because the current is smaller at a high voltage. |
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Why do resistors get hot when current passes through them? |
Charges hit the stationary ions in the resistor transferring energy as heat |
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How does a filament lamp work? |
Current passes through a filament lamp and charges hit the stationary ions transferring energy as heat. When enough heat is transferred the wire glows hot. |
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Why is the filament the only wire that glows in the lamp? |
The filament wire is the thinnest wire, thin wires have a higher resistance so more energy is transferred.
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What is a light dependent resistor and how does it work? |
LDR changes resistance depending on the light. Low light = high resistance so the lamp glows. |
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What is a thermistor and how does that work? |
A thermistor changes resistance depending on the temperature. Low temperature means high resistance so heat is generated. |
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In series, what happens to the potential difference (voltage)? |
It is shared between components |
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In parallel what happens to potential difference? |
It is equal anywhere in the circuit |
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What happens to current in series? |
It is equal everywhere |
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What happens to current in parallel? |
It is shared |
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If I add two resistors in series, what happens to the total resistance? |
It is the sum of each resistor (adds up) |
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If I add two resistors in parallel, what happens to the total resistance? |
It is less than one resistor by itself. |
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What do AC and DC mean? |
Alternating current and direct current |
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How do you generate electricity? |
Rotate a magnet in a coil of wire to induce a voltage |
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What is the name of the process used to generate electricity? |
Electromagnetic induction |
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What kind of electricity does electromagnetic induction create? |
AC |
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What are the four factors affecting the amount of electricity that can be generated? |
Add an iron core, increase the strength of the magnet, increase the speed of the rotation, increase the number of turns on the coil of wire. |
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What is a transformer? |
Something that changes the voltage |
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Describe how transformers work |
A coil of wire wrapped around an iron core. The primary coil induces a changing magnetic field in the core which induces a voltage in the secondary coil. The number of turns on the wire affect the size of the voltage induced. |
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Do transformers use AC or DC? |
AC |
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How do motors work? |
A coil of wire has a current which interacts with a magnet which induces the wire to move (force) |
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What is a commutator? |
it reverses the current every half turn. |
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Each half of the coil of wire moves.... |
In opposite directions |
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What happens if you reverse the magnetic field in a magnet? |
It moves the opposite way. |
