OCR 21st Century Combined Science P3

• Created by: kokokeisy
• Created on: 24-04-18 09:13
Define an Electrical Current.
The rate of flow of electrical charge.
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Unit of current?
(A) Ampere
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Define a Potential Difference/Voltage
The driving force that pushes charge around a curcuit
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Unit of P.D/Voltage
(V) Volt
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Define a Resistance
Anything that resists the flow of charge.
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Unit of Resistance
Ohms
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What components in a curcuit will cause the current to increase and how?
If the potential difference increases whist the resistance stays the same
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What components in a circuit will cause the current to decrease and how?
If the resistance is increased but the potential difference stays the same.
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What sources in a curcuit causes charge to flow?
A Battery
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Equation for Charge?
CHARGE=CURRENT X TIME (Q=I%T)
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Equation for Potential Difference?
POTENTIAL DIFFERENCE = CURRENT X RESISTANCE (V=IR)
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What component can you use to investigate the factors that effect resistance?
The length of the wire; Compare the resistance of each wire with different lengths and draw a graph to show it.
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Whats a diode?
Semiconductor material which lets current flow in one diretion.
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Uses of a diode
Used in electronical curcuits, radio recievers, and to get direct current.
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Uses of D.C Circuits? (Direct Current)
To tests LDRs and Thermistors
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Whats a LDR? (Light Dependant Resistor)
A resistor thats dependent on the intsesity of light.
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In a LDR, whens the resistance at its highest ?
In darkness.
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In a LDR, whens the resistance at its lowest.?
When theres a high intensity of light
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Uses of LDR?
Automatic night lights, Outdoor Lighting, Burglar Detectors
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Whats a Thermistor?
A resistor thats dependent on the temperature.
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In a thermistor, whens the resistance at its lowest?
When its hot
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in a thermistor, whens the resistance at its highest?
When its cold.
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How can you test the resistance of a thermistor?
Placing it in hot and cold water and measuring the resistance.
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Uses of a thermistor?
Temperature detectors, Thermostats, Irons, Car engines.
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Uses of a sensing circuit?
To turn on or increase the power of components depending on the conditions theyre in.
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What does an electrical current do?
It transfers energy from a power supply.
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What does a power supply do\?
It does work on a charge and so transfers energy to it
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What does Charge do?
It transfers energy to a component as it passes through it, and doing work AGAINST the resistance of the compoment.
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What is the IV Characteristic of a Fixed Resistor?
As the current and voltage increases, the RESISTANCE DECREASES
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What is the IV Characteristic of a Filament Lamp?
As the voltage and current increases, the temperature increases, causing the current to DECREASE and the resistance to INCREASE
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What is the IV Characteristic of a Diode?
Current only flows in ONE DIRECTION, so the opposite direction has a very HIGH resistance whilst the other side has a LOW resistance.
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What is the IV Characteristic of a Thermistor?
As the temperature increases, the resistance decreases.
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What is the IV Characteristic of a LDR?
The higher intensity of light, the lower the resistance.
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What are Power Ratings for?
They tell you the rate that energy is transferred to devices from a power supply.
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What is Power measured in?
W (Watts)
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What causes a high amount of power and How?
A high potential difference; it causes charge to have MORE energy, meaning it can move FASTER and transfer MORE energy in a GIVEN TIME.
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Why would you get a larger total p.d in a series circuit than in a parallel circuit?
Each charge in the circuit passes through each cell and gets a 'push' from each one.
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Uses of Parallel Circuits and why?
Cars or Household Electrics, because you can switch things on and off seperately.
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Where do you place ammetres and voltmeters in circuits?
Place Ammetres in SERIES and Voltmeters in PARALLEL.
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What is a Series Circuit?
A circuit which has no branches, and the current can only flow in one path.
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What is the potential difference, resistance, and the current in a series circuit?
The CURRENT is the same way round the whole circuit, the P.D is SHARED between components, Resistance ADD TOGETHER.
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Whats the Equation for the P.D across a SERIES circuit?
V=V1+V2
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Whats the Equation for the RESISTANCE in a SERIES circuit?
R=R1+R2+R3
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Whats the Equation for the Current in a SERIES Circuit?
I=I1=I2=I3
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What is a Parallel Circuit?
A circuit with branches where current can flow in.
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Whats the Potential Difference, REsistance and the current in a Parallel Circuit?
The Potential difference is the SAME across all components, the Current in the branches ADDS UP TO THE TOTAL current LEAVING the cell,
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WHats the equation for Potential Difference in Parallel Circuit?
V1=V2=V3
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Whats the equation for the Current in a Parallel Circuit?
I = I1 + I2
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What does the net resistance of a circuit depend on? (with two or more components)
The resistance of the components.
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Poles of Magnets?
North and South
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Define a Magnetic Field
a region where other magnets or magnetic fields experience a force (MAGNETIC EFFECT)
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Define the Magnetic Effect
Non-contact force that occurs due to interacting magnetic fields
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How do you know if theres a strong magnetic field?
If the lines are close together in the diagram.
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How do you know if theres a weak magnetic field?
If the lines are far apart in the diagram
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Where are the magnetic fields strongest?
At the poles of the magnet
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What forces can there be between two magnets ?
Attraction and Repulsion
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What is a compass and how does it work?
A tiny bar magnet where the north pole of the magnet attracts itself to a south pole anywhere near it. the compass points in the DIRECTION of the MAGNETIC FIELD it i in
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Why does a compass always point north when not near a magnet?
The Earth Generates its own magnetic field in the core of the Earth; its magnetic
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Other cards in this set

Unit of current?

(A) Ampere

Card 3

Front

Define a Potential Difference/Voltage

Card 4

Front

Unit of P.D/Voltage

Card 5

Front

Define a Resistance