P2 Electricity Flashcards
<p>What is <b>electrical current</b>?</p>
<p>Electrical Current is the flow of electrical charges</p>
<p>What is current measured in?</p>
<p>Current is measured in Amperes (A)</p>
<p>How do you calculate <b>flow of charge</b>?</p>
<p>Flow of Charge (C) = Current (A) x Time (s)</p>
<p>Q = It</p>
<p>What is an <b>Electrical Insulator</b>?</p>
<p>An electrical insulator is a material that doesn't allow electric currents to pass through it</p>
<p>What is an <b>Electrical Conductor</b>?</p>
<p>An electrical conductor is a material that allows electric currents to pass through it</p>
<p>Why can't electrical insulators conduct electricity?</p>
<p>Electrical Insulators have no free electrons</p>
<p>This means no charges are free to move and carry a current</p>
<p>What is <b>Potential Difference</b>?</p>
<p>Potential difference is the amount of energy that charge carriers have between two different points in a circuit</p>
<p>What is Potential Difference measured in?</p>
<p>Potential Difference is measured in Volts (V)</p>
<p>How do you calculate Potential Difference?</p>
<p>Potential Difference (V) = Current (A) x Resistance (Ω)</p>
<p>V = I x R</p>
<p>How do you calculate <b>Electrical Energy Transferred</b>?</p>
<p>Energy Transferred (W) = Potential Difference (V) x Charge (C)</p>
<p>E = V x Q</p>
<p>What variables effect the size of current?</p>
<ol><li>Resistance - If resistance increases, the current will decrease</li><li>Potential Difference - If the Potential Difference increases, the current will increase</li></ol>
<p>What is Resistance measured in?</p>
<p>Resistance is Measured in Ohms (Ω)</p>
<p>What is Power?</p>
<p>Power is the rate of energy transfer to a component</p>
<p>What is the size of current affected by?</p>
The size of current is affected by two things:
<ol><li>The resistance: If the resistance is increased, the current will decrease</li><li>The potential difference: If the potential difference is increased the current will increase</li></ol>
<p>How do you calculate resistance?</p>
<p>Resistance = Voltage/Current</p>
<p>R=V/I</p>
<p>What do you use to measure voltage?</p>
<p>Voltmeter</p>
<p>What do you use to measure current?</p>
<p>Ammeter</p>
<p>What is Ohm's Law?</p>
<p>Voltage = Current × Resistance</p>
<p>V=IR</p>
<p>Why does the I-V charicteristic of a bulb curve?</p>
<p>The I-V characteristic of a filament bulb curves because temperature rises. As temperature rises, so does resistance. As a result, the rate of increase of the current decreases and a greater change in the potential difference is required to cause a change in the current</p>
<p>How do you calculate electrical power?</p>
<p>Power = Current × Voltage</p>
<p>P = I × V</p>
<p>Power = Current2 × Resistance</p>
<p>P=I2R</p>
<p>How do you calculate Total Energy Transferred?</p>
<p>Energy Transferred = Power × Time</p>
<p>E = P × t</p>
<p>What are <b>Ohmic Conductors</b>?</p>
<p>Ohmic Conductors are conductors that obey Ohm's Law</p>
<p>The current through an Ohmic Conductor is directly proportional to the potential distance across as resistor</p>
<p>How do you calculate <b>Electrical Power</b>?</p>
<p>Power = current x Potential Difference</p>
<p>P = IV</p>
<p>Power = current2 x resistance</p>
<p>P = I2R</p>
<p>How do you calculate the total resistance of resistors in a series circuit?</p>
<p>Their total resistance is calculated by adding up the resistances of each individual resistor eg. R = R1 + R2 + R3 ...</p>
How do you calculate total resistance in Parallel circuits?
1/Total Resistance = 1/Resistor1 + 1/Resistor2 ...
How do you calculate electrical work done per second?
Energy Transferred = Power x Time
E=Pt
Energy Tranfered = Potential Difference x Charge
E=VQ
What is the potential difference across the mains power supply in the UK?
230 V
What remains constant for an ohmic conductor?
Resistance
What is a Diode?
A diode is a component that only allows current to flow through it in one direction
What are Rectifiers?
A rectifier is a component that turns alternating current (repeatedly changes direction) into a direct current (one direction)
Diodes act as rectifiers as they block the alternating current when it changes direction.
What is a Thermistor?
A Thermistor is a component where Resistance changes with its temperature
Increasing temperature decreases resistance
What is a LDR?
An Light Dependent Resistor changes resistnace with light intensity
Increasing light Intensity decreases resistance
What is Alternating Current?
Alternating current is when the electric current repeatedly changes direction
What is the frequency and current of the mains electricity supply in the UK?
The mains electricity supply has a frequency of 50Hz and is about 230 V
What is Direct current?
Direct current is when the electric current only flows in one direction
What are the three wires in a cable?
- Neutral Wire
- Live Wire
- Ground Wire
What colour is the Neutral Wire?
Blue
What is the voltage of the Neutral Wire?
0 V
What is the purpose of the Neutral Wire?
The Neutral wire completes the circuit and carries the current away from the appliance
What colour is the Live Wire?
Brown
What is the voltage of the Live Wire?
230 V
What is the purpose of the Live Wire?
The Live wire provides the alternating voltage from the mains electricty supply
What colour is the Earth Wire?
The Earth Wire has Green and Yellow stripes
What is the voltage of the Earth Wire?
0 V
What is the pupose of the Earth Wire?
The Earth wire is a safety wire to stop the appliance becoming live
How do you calculate power?
Power = Potential Difference × current
P=IV
Power = Current2 × Resistance
P=I2R
How do you calculate Energy transferred?
Energy Transferred = Power × Time
E=Pt
Energy Transferred = Charge Flow × Voltage
E=QV
What voltage is produced in power stations?
25,000 V
What are Step Up Transformers?
Step Up Transformers increase the Voltage from 25,000 V to 400,000 V
This is to reduce the current and reduces the heat lost when being transported. This increases the efficiency of the National Grid system
What are Step Down Transformers?
Step Down Transformers get the electricity to 230 V so its safe
What are Fuses?
Fuses are an electrical component that contain a wire which melts if the current flowing through a circuit is too high
This breaks the circuit which stops the flow of electrical current
What are Circuit Breakers?
Circuit Breakers are devices that switch of the flow of current if the current is above a certain value
What are the advantages of using ciruit breakers over fuses?
Fuses only work once. Once blown, they must be replaced We can reset circuit breakers. Circuit breakers also break circuits faster than fuses. This reduces the risk of getting an electric shock even more
What are Fuse Ratings?
Fuse Ratings tell us the the level where a fuse will begin to melt
How does the Earth Wire work when an appliance develops a fault?
The Earth wire is a low resistance wire that connects the metal case of an appliance to the ground If the casing is touched by a wire, the current will flow through the Earth Wire As the wire has low resistance, a high current will flow through it and break a fuse in the appliance. This will stop the current and make the device safe
How does an object become charged?
An object becomes charged after gaining or gaining electrons
How are electrical sparks produced?
Sparks are produced when there is a high potential difference between two objects
This high potential difference causes a rapid transfer of charge
Energy is stored in the electrostatic sotre which produces a charge
