# Electricity

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• Created by: lh1002
• Created on: 18-05-16 20:27
What is the equation for power loss? Include units.
Power loss (W) = current (A)² x resistance ( )-- (P=I²R)
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What is the equation for energy transferred (using charge)? Include units.
Energy transferred (J) = charge (C) x voltage (V)-- (E=QV)
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What is the equation for energy transferred (using power)? Include units.
Energy transferred (J) = power (W) x time (s)-- (E=Pt)
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What is the equation for power? Include units.
Power (W) = current (A) x voltage (V)-- (P=VI)
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What is power?
'The rate of doing work'
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On an oscilloscope, what do AC and DC currents look like?
AC DC
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What is the name and colour of each wire in a plug?
Earth wire (green and yellow sTriped), neutral wire (bLue), live wire (bRown)
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What is the UK mains supply voltage and frequency?
230V, 50Hz
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Is a voltmeter connected in series or in parallel?
In parallel
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Is an ammeter connected in series or in parallel?
In series
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What does DC stand for and what does it mean?
Direct Current - current only flows in one direction
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What does AC stand for and what does it mean?
Alternating Current - when the current changes direction
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What are the 4 factors which affect resistance?
Material e.g. copper has lower resistance than steel. Length - longer wires have greater resistance. Thickness - smaller diameter wires have greater resistance. Temperature - heating a wire increases its resistance.
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What is resistance and what is it measured in?
Anything that will resist a current, Ohms ( )
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What is the equation for resistance?
Resistance = voltage / current-- (R= V/I or V=IR)
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What is another name for voltage?
Potential difference
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What is charge and its equation?
The flow of current, charge = current x time-- (Q=It)
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What does LED stand for, what does it do and what is its symbol?
Light Emitting Diode, a diode which glows when electricity passes through
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What does a light dependent resistor do and what is its symbol?
The resistance decreases with increasing light intensity
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What does a thermistor do and what is its symbol?
The resistance decreases with increasing temperature
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What does a fuse do and what is its symbol?
Protects the circuit incase the current is too high
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What does a diode do and what is its symbol?
Allows electricity to flow in one direction only
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What does a variable resistor do and what is its symbol?
Restricts electrical flow to a chosen amount
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What is a human's audible range?
20Hz - 20,000Hz
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What is the national grid?
The National Grid is a system of cables and transformers transferring electrical power from power stations to consumers.
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What does a step up transformer do?
Step-up transformers are used to increase the voltage from the power station to the transmission cables and decreases the current
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What does a step down transformer do?
Step-down transformers are used to decrease, to a much lower value, the voltage for domestic use and increases the current.
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What is a transformer?
A transformer is an electrical device that changes the voltage of an alternating current (ac) supply, such as the mains electrical supply.
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Why does the current need to be decreased before going up to the transmission cables?
When a current flows through a wire some energy is lost as heat. The higher the current, the more heat is lost. To reduce these losses, the National Grid transmits electricity at a low current.
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ADVANTAGES: less expensive, easier to repair, don't need casing, DISADVANTAGES: spoils landscape, health issues
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What are all the advantages and disadvantages of the underground National Grid?
ADVANTAGE: hidden so doesn't spoil landscape, DISADVANTAGES: expensive, expensive to repair, water proofed, casing needed to prevent them getting hot
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What is static electricity?
Static electricity is where charge doesn't move because it has been created on an insulator
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What is an electric field?
Any area in which an electric charge experiences a force- a charged object creates an electric field around itself.
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What happens when a transparent rod and cloth are rubbed together?
Both the rod and the cloth are neutral to begin. Friction happens and electrons (-) move from the rod to the cloth which makes the rod positively and the cloth negatively charged.
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What happens differently with an opaque rod in static electricity?
It does the opposite to the transparent rod- electrons move from the cloth to the rod instead, therefore the cloth is now positive and the rod is negative
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What are the dangers of static electricity?
Builds up in clouds, a spark forms from the ground & cloud- lightning; a spark can ignite flammable gases / a high concentration of oxygen & cause an explosion; touching something with a big charge causes electric shock- can burn or even stops heart
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What happens when two objects carry the same charge?
They repel eachother
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What happens when two objects carry a different charge?
They attract eachother
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How strong is the electric field when the charged object is close? Far away?
The electric field is strongest close to the charged object. The further away from the charged object, the weaker the field.
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What happens when a second charged object is placed in the field?
It experiences a force. The force gets stronger as the distance between the objects decreases.
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What are the lines on an electric field diagram?
Lines of force
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What does it mean when the lines on an electric field diagram are close together?
The force is strong
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What does the direction of the arrows on an electric field diagram mean?
The direction of the arrow on the electric field line shows the direction in which a positively charged particle placed within the field will move. Negatively charged particles, for example electrons, will move in the opposite direction to the arrow.
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Generally, what is the current, voltage and resistance of each component in a series circuit?
There is the same current through each component; the total voltage of the power supply is shared between the components; the total resistance of two components is the sum of the resistance of each component.
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Generally, what is the current, voltage and resistance of each component in a parallel circuit?
The voltage across each component is the same; the total current through the whole circuit is the sum of currents through the separate components; the total resistance of two resistors is less than the resistance of the smallest individual components
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What does each wire in a plug do?
The live wire carries the alternating potential difference from the supply. The neutral wire completes the circuit. The earth wire is a safety wire to stop the appliance becoming live.
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On a graph, what does the current vs voltage look like through a resistor?
The current through a resistor (at a constant temperature) is directly proportional to the potential difference across the resistor. This means that the resistance remains constant as the current changes. This is said to follow Ohm's Law.
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What is Ohm's Law?
The result that the current through a resistor is directly proportional to the voltage across the resistor at a constant temperature.
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On a graph, what does the current vs voltage look like through a filament lamp?
The resistance of a filament lamp increases as the temperature of the filament increases
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On a graph, what does the current vs voltage look like through a diode?
The current through a diode flows in one direction only. The diode has a very high resistance in the reverse direction
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## Other cards in this set

### Card 2

#### Front

What is the equation for energy transferred (using charge)? Include units.

#### Back

Energy transferred (J) = charge (C) x voltage (V)-- (E=QV)

### Card 3

#### Front

What is the equation for energy transferred (using power)? Include units.

### Card 4

#### Front

What is the equation for power? Include units.

What is power?