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65 Cards in this Set
- Front
- Back
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Describe What is Meant by an Electric Current |
Electric Current = Flow of Electrical Charge (electrons) Around a Circuit.
The Current Flows from the Negative End of the Cell to the Positive End. However, Scientists Draw the Current in the Opposite Direction called the Conventional Current. (Positive to Negative)
Unit = Ampere (A)
To Measure Current = Ammeter |
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Describe the Pattern of Current Flow in a Series Circuit |
In a Series Circuit, the Current is the Same all the way around. |
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Draw a Series Circuit |
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Draw a Parallel Circuit |
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Describe the Pattern of Current Flow in a Parallel Circuit |
In a Parallel Circuit, the Current Splits and is Shared between the Branches. The Current in the Branches Adds up to the Total Current Leaving the Cell. |
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Explain What is Meant by Potential Difference (Voltage) |
The Current is when Electrons Flow and Transfer Energy to the Components in the Circuit.
A Potential Difference of 1 Volt tells us that 1 Joule of Energy is transferred for Each Coulomb of Charge (electrons) that is Moving through the Circuit.
To Measure Voltage = Voltmeter |
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Describe Potential Difference in Series Circuits |
In Series Circuits, the Total Potential Difference of the Cell is Shared Between the Components Potential Difference is Split between Components. |
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Describe the Potential Difference in Parallel Circuits |
For Components Connected in Parallel, the Potential Difference across Each Component is the Same. |
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Work out the Potential Difference |
The Voltage across the Bottom Branch must be the Same as the Branch Above |
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Draw the Component Symbols (14) |
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When Can Electrical Charge Flow? |
In a Closed Circuit, Electrical Charge Can Only Flow if there is a Potential Difference |
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What is the Formula that Links Charge Flow, Current and Time |
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Describe the Energy Transfers in a Circuit |
P |
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Describe What is Meant by a Battery |
Battery = 2 or more Cells Connected. The Cells in a Battery Must be Connected in the Same Direction. If Batteries are Facing the Opposite Direction, Potential Difference = 0V |
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How Would you Calculate the Potential Difference Produced by a Battery? |
Potential Difference of Battery = Sum of Potential Difference of Cells |
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What is Electrical Charge? |
Electrical Charge is Measured in Coulombs (C). 1 Amp = 1 Coulomb of Charge per Second The Size of the Electric Current is the Rate of Flow of Electrical Charge. |
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Calculate the Total Energy Transferred by a Component
Write the Formula that Links Energy Transferred, Charge Flow and Potential Difference |
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Describe What is Meant by Resistance |
Resistance is anything in the Circuit which Slows the Flow of Current Down.
Unit = Ohm
The Greater the Resistance Across a Component, the Smaller the Current |
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What is an Ohmic Conductor? |
Ohmic Conductors are Wires or Resistors.
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Describe the Resistance of Ohmic Conductors Using an IV Characteristic |
The Resistance of Ohmic Conductors is Constant and Doesn't Change with the Current. At a Constant Temperature, the Current Flowing Through an Ohmic Conductor is Directly Proportional to Potential Difference, so you get a straight line. |
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Describe the Resistance of a Filament Lamp Using the IV Characteristic |
When Current Flows Through a Filament Lamp, it Transfers some energy to the Thermal Energy Store of the Filament which Heats Up. Resistance Increases with Temperature. In a Filament Lamp, the Current is NOT Directly Proportional to Potential Difference. As the Current Increases, the Temperature of the Filament Increases, so the Resistance Increases. As the Potential Difference Increases, the Current No Longer Increases as Much - hence the Curve. |
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Describe the Resistance in a Diode Using IV Characteristics |
Current will only Flow Through a Diode in 1 Direction.
The Diode has a Very High Resistance in the Reverse Direction |
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Why are Diodes Useful? |
Diodes are Extremely Useful for Controlling the Flow of Current in Circuits. |
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Describe an LED ( Light-Emitting Diode) |
An LED gives off Light when a Current Flows Through and Only Allows Current to Flow in 1 Direction. LEDs are an Extremely Energy-Effecient Source of Light. |
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Describe the Resistance in Series Circuits |
In Series Circuits, the Resistance In Resistors Adds Together. This is because the Current has to Pass through Each Resistor in Turn. It cannot Bypass any Resistor. |
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Describe the Resistance In Parallel Circuits |
The Total Resistance of 2 Resistors in Parallel is Less than the Resistance of the Smallest Individual Resistor. With 2 Resistors in Parallel, we have 2 Pathways for the Current to Take. |
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What is the Symbol for a Light-Dependent Resistor (LDR)? |
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Describe How the Resistance of an LDR Changes in Light and Dark Conditions |
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Write a Method on How to Investigate the Factors Affecting the Resistance of Electrical Circuits
REQUIRED PRACTICAL 3
E.g. How Wire Length Affects Resistance |
Voltmeter = Must be Placed in Parallel to What your Investigating.
Ammeter = Must be Placed in Series.
1) Attach a Crocodile Clip to the Wire, level with 0cm on the Ruler. Attach the Second Clip 10cm Away from the First clip. Write Down the Length of the Wire between the Clips.
2) Close the Switch and Record the Current and Voltage. Open the Switch and Move the Second Crocodile Clip Another 10cm Along the Wire. Close the Switch Again and Record the Current, Voltage and New Length.
3) Repeat this for a Number Different Lengths of the Wire and Calculate the Resistance using the Formula.
Plot a Graph of Resistance (y-axis) Against Wire Length (x-axis) and Draw a line of Best Fit.
Graph = Straight Line through Origin. Resistance of Wire is Directly Proportional to Length. |
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Describe The Errors that Can Occur During REQUIRED PRACTICAL 3 : Wire Length on Resistance |
Zero Error:
1) If the Graph doesn't go through the Origin = the First Clip wasn't Attached Exactly at 0cm on the Ruler. This is a Zero Error.
A Zero Error is a Reading on a Measuring Instrument when the Value Should be 0. This is a Systematic Error and so we cannot correct it by Carrying out Repeats.
SOLUTION : Subtract the Zero Error from all of Our Readings.
Heating Effects:
The Wire may Heat Up During the Experiment which will Affect its Resistance.
SOLUTION: Only Turn on the Current When Taking Readings. Turn off the Current between Readings to let the Circuit Cool Down. |
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How do you Calculate Energy Transferred by Appliances? What is the Formula that Links Energy Transferred, Power and Time? |
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How do you Calculate the Power of Components? Write the Formula that Links Power, Voltage and Current |
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How do you Calculate the Power of Components? Write the Formula that Links Power, Current and Resistance |
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What are the 2 Types of Electricity Supplies? |
Alternating Current (AC) Direct Current (DC) |
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Describe Direct Current (DC) |
Direct Current is a Current that is Always Flowing in the Same Direction. The Current from a Cell is a Direct Current. |
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Describe Alternating Current (AC) |
In AC Supplies, the Current is Constantly Changing Direction. The Benefit of AC is that it is Very Easy to use a Transformer to Increase or Decrease the Potential Difference. The UK Mains Supply is an AC Supply with a Potential Difference of 230V and a Frequency of 50 Hertz (Hz). |
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What is the Frequency and Potential Difference of UK Mains Electricity? |
The UK Mains Supply is an AC Supply with a Potential Difference of 230V and a Frequency of 50 Hertz (Hz). |
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What Can we Use to See the Pattern of an Electric Current? |
Oscilloscope = Alternating Current The Potential Difference is Rising and Falling |
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How Do you Work Out the Maximum Potential Difference from an Oscilloscope? |
The Height of the Peak Tells us the Maximum Potential Difference. |
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What Does a Direct Current Look Like on an Oscilloscope? |
In a Direct Current, the Potential Difference Doesn't Change |
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How are Most Electrical Appliances Connected to the Mains Supply? |
Most Electrical Appliances are Connected to the Mains Supply by Three-Core Cables.
There are 3 Wires.
Each Wire is Made of Copper which is a Good Conductor of Electricity.
Each Wire is Coated in Plastic which does not Conduct Electricity. |
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What is the Function of the Brown Wire in a Three-Core Cable? |
Brown Wire = Live Wire.
The Live Wire Carries the Alternating Potential Difference at 230V from the Mains Supply
The Live Wire is Connected to a Fuse in a Plug. The Live Wire is Extremely Dangerous and Could Easily be Fatal if Touched. |
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What is the Function of the Blue Wire in a Three-Core Cable? |
Blue Wire = Neutral Wire. The Neutral Wire Completes the Circuit and Carries Away Current - Electricity Flows In through the Live Wire and Out through the Neutral Wire. It has a Potential Difference of 0V Compared to the Live Wire. |
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What is the Function of the Green and Yellow Wire in a Three-Core Cable? |
Green/Yellow Striped Wire = Earth Wire
The Earth Wire is a Safety Wire used to Stop the Appliance from Becoming Live. |
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Draw a Circuit Diagram of a Simple Circuit Wired to the Mains Supply |
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Describe Why a Live Wire is Still Dangerous Even When the Switch is Open |
Even if a Plug Socket or Light Switch is Turned Off ( the Switch is Open) there is still a Danger of an Electric Shock.
Even Though there is No Current Flowing, the Live Wire Still has Potential Difference of 230V. The Potential Difference of the Earth is 0V so if Someone Touched the Live Wire, a Current Would Flow through the Person into the Earth and they'd be Electrocuted. |
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Why are Appliances with Metal Cases Dangerous and How Does the Earth Wire Prevent You from Getting an Electric Shock? |
Appliances with a Metal Case can be Very Dangerous. This is because if the Live Wire Comes Loose and Touches the Metal Case, the Case can Become Live which Could give Someone a Fatal Electric Shock if they Touched it.
To Prevent this, the Metal Case is Attached to the Earth Wire. The Earth Wire is Connected into the Ground with a Metal Rod. If the Case Becomes Live, a Huge Current Flows to the Earth. The Fuse Melts and Shuts off the Current which Prevents anyone from getting an Electric Shock. |
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Describe How Different Domestic Appliances Transfer Energy E.g. Fan, Kettle |
In a Kettle, Electrical Energy from the Mains AC Supply Is Transferred to Thermal Energy. In a Fan, Electrical Energy is Transferred to the Kinetic Energy of the Electric Motors. |
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What is the National Grid? |
The National Grid is a System of Transformers and High-Voltage Cables.
The National Grid Transfers Electrical Energy from Power Stations to Consumers. Step-up Transformers Increase the Potential Difference. This Reduces Energy Loss in the Transmission Cables. Step-Down Transformers Reduce the Potential Difference before the Electricity Passes to Homes. For a Given Power, Increasing the Potential Difference Decreases the Current, which Decreases the Energy Lost by Heating the Wires and the Surroundings. |
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Describe the Role of Step-up and Step-Down Transformers in the National Grid |
Step-up Transformers Increase the Potential Difference. This Reduces Energy Loss in the Transmission Cables. Step-Down Transformers Reduce the Potential Difference before the Electricity Passes to Homes. |
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Describe How Electricity Production has to Meet Demands via the National Grid |
Throughout the Day, Electricity Usage (Demand) Changes. Power Stations can Predict when the Most Electricity will be used. Demand Increases when People get up in the Morning, Come Home from School/ Work and when it Starts to get Dark or Cold Outside. Popular Events like a Football match on TV could also Cause a Peak in Demand. |
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What is the Difference between Conductors and Insulators? Give Examples |
Metals are Good Conductors of Electricity. Electrons can Easily Flow through Metals. Objects Such as Plastic, Glass, Cloth are Insulators. They do Not Conduct Electricity because Electrons Cannot Move Through Insulators. |
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Describe How Static Electricity is Caused |
When Certain Insulating materials are Rubbed Together, Negatively Charged Electrons are Rubbed off 1 Material and onto the Other.
This will Leave the Materials Electrically Charged. The Material that Gains Electrons Becomes Negatively Charged. The Material that Loses Electrons is Left with an Equal Positive Charge.
Which Way the Electrons are Transferred Depends on the 2 Materials Involved.
E.g. When we Rub Plastic onto a Cloth, Electrons Move from the Plastic onto the Cloth |
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Describe How Static Electricity can Cause Sparking |
As Electric Charge Builds up on an Object, the Potential Difference between the Object and the Earth (at 0V) Increases. If the Potential Difference is Large Enough, Electrons can Jump Across the Gap between the Charged Object and the Earth Causing a Spark. |
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Describe How 2 Charged Objects Exert a Force on Each Other |
When 2 Electrically Charged Objects are Brought Close Together, they Exert a Force on Each Other.
Electrostatic Attraction/ Repulsion is a Non-Contact Force: the 2 Objects are not Touching.
Oppositely Charges are Attracted to Each Other.
Same Charges Repel. |
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What is an Electric Field? |
A Charged Object Creates an Electric Field around itself. The Closer to the Object you get, the Stronger the Field is. The Further Away from the Charged Object, the Weaker the Field. |
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Draw the Electric Field Pattern for an Isolated Charged Sphere |
Electric Field Lines go from Positive to Negative. They're always at a Right Angle to the Surface. The Closer Together the Lines are, the Stronger the Field is. |
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Draw the Electric Field Pattern for a Positively Charged Sphere |
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Draw the Electric Field Pattern for a Negatively Charged Sphere |
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Describe How Charged Objects in an Electric Field Feel a Force. |
When a Charged Object is Placed in the Electric Field of Another Charged Object, it Experiences a Force.
The Force is Caused by the Electric Fields of Each Charged Object Interacting with Each Other.
The Force of an Object is Linked to the Strength of the Electric Field it is in. The Force Gets Stronger as the Distance between the Objects Decreases. |
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Describe How Sparking Can be Explained by Electric Fields |
Sparks are Caused when there is a High Potential Difference between a Charged Object and the Earth. (Or an Earthed Object) A High Potential Difference Causes a Strong Electric Field between the Charged Object and the Earthed Object. The Strong Electric Field Causes Electrons in the Air Particles to be Removed (Ionisation). Air is Normally an Insulator, but when it is Ionised it is much more Conductive, so a Current can Flow Through it. This is the Spark. |
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Write a Method to Investigate the IV Characteristics of Circuit Components REQUIRED PRACTICAL 4 |
1) Set up the Test Circuit as Shown in the Diagram.
2) First Calculate the Voltage and Current through the Component (e.g. Resistor) and Record these Values in a Table.
3) Then Adjust the Variable Resistor and Record the New Readings on the Voltmeter and Ammeter. Repeat this Several times to get a Range of Readings.
4) Then Swap Over the Wires Connected to the Battery, so the Direction of the Current is Reversed. Both the Ammeter and Voltmeter Should Now Have Negative Values.
5) Continue Taking Several Readings of the Potential Difference and Current.
6) Plot a Graph of Current Against Voltage for the Component. This is the IV Characteristic. |
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Why Does the National Grid Produce Less than Halve of the Total Energy that they Could when Operating at a Maximum Output? |
To Provide Spare Capacity in Case of Power Station Emergency Shut-down. To Provide a Spare Capacity to Compensate for Unreliable Renewable Resources. To Conserve Fuel Reserves. |
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When the Total Power Input to a Motor was 5W the Motor Could Not Lift the 2.5N Weight State the Efficiency of the Motor |
The Efficiency is 0% |
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Why Do we Wear Gloves and Other Things as a Safety Precaution when Handling Radioactive Materials? |
To Prevent Contamination and to Stop the Radioactive Material from Penetrating the Body - Causing Cell Damage. |
