31101147
Description
Flashcards by Malachy Moran-Tun, updated more than 1 year ago
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Created by Malachy Moran-Tun
about 4 years ago
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| Question | Answer |
| What is a Build Up of Static Caused by? | > Insulating materials rubbed together > Friction causes negatively charged electrons to be transferred > Materials have equal electronic charge > Always the negative electrons that move |
| How do Electronically Charged Objects Exert Forces on Eachother? | Like charges Repel Opposite charges Attract (← + + →) (← - - →) (+ →← -) |
| Why can Electrically Charged Objects Attract Uncharged Objects? | > Charges on the surface on the uncharged object (e.g. a wall) can move slightly > Charged object (e.g. a balloon) attracts / repels the charges on the surface > Surface of the uncharged object becomes slightly charged, which attracts the oppositely charged object |
| What are Electrostatic Sprayers and How do they Work? | > Spray gun is charged, which charges up small drops of paint / insecticide > Each drop repels the others (since they have the same charge), so you get a fine, even spray > Object to be painted is given the opposite charge to the paint gun > Spray paint is attracted to the object, meaning an even coat is applied around all surfaces |
| How are Sparks Produced by Static? | > As an electric charge builds up, the potential difference increases between the object and the earth > If the voltage gets large enough, electrons can jump across the air - this is a spark > They can also jump to any earthed conductor (such as you) > Usually this is small, but lightning ain't small |
| How can a build up of Static Electricity be Dangerous? | > Refuelling cars - as fuel flows out, static can build up, which can lead to a spark and therefore a big ol' boom > Static on Aeroplanes - friction is built up between the air and the plane, causing it to become charged, interfering with communication equipment > Lightning - raindrops and ice collide with eachother, leaving the cloud positively charged, creating a huge voltage and a big spark, which can start fires |
| How can a Build Up of Static Charge be Prevented? | > Connecting a charged object to the ground using a conductor (earthing) > Provides an easy route for static charges to travel to the ground, meaning no charge can build up |
| What are Electric Fields? | > Created around any electrically charged object > Region around the object where, if a second object is placed inside it, a force is exerted on both of the charges > Closer the objects get to eachother, the stronger the force is |
| How are Electric Fields Represented? | |
| What are Uniform Electric Fields? | > When two charged objects are placed in eachother's electric field, they both feel a force > Force is caused by the electric fields interacting > If the field lines between the charged objects point in opposite directions, the field lines push against eachother, so the object repel > This creates a uniform field |
| Fill in the Blanks: When a _____ moves an object through a distance, ____ is ____ on the object and _____ is transferred | When a FORCE moves an object through a distance, WORK is DONE on the object and ENERGY is transferred |
| What Equation links Word Done, Force, and Distance Moved in the Direction of the Force? | Work Done (J) = Force (N) × Distance Moved in the Direction of the Force (m) or E = Fd |
| What is Power? | > Rate of Energy Transfer > How much Work is Done per Second |
| What Equation links Power, Work Done, and the Time Taken? | Power (W) = Work Done (J) ÷ Time Taken (s) or P = E ÷ t |
| What is Current? | Flow of Electrical Charge |
| What Unit is Current Measured in? | Amps / Amperes (weirdos) / A |
| What is Potential Difference? | Voltage "Driving force" that pushes the charge around |
| What Unit is Potential Difference Measured in? | Volts / V |
| What is Resistance? | Anything that slows the flow of current down |
| What is Resistance Measured in? | Ohms / Ω |
| What Equation Links Charge, Time and Current | Charge (C) = Current (A) × Time (s) Q = It |
| What Equation Links Charge Moved, Potential Difference and Energy Transferred? | Energy Transferred (J) = Charge Moved (C) × Potential Difference (V) E = QV |
| What Equation Links Potential Difference, Resistance and Current? | Potential Difference (V) = Current (A) × Resistance (Ω) V = IR |
| Generally, what does Temperature do with Resistance in Electrical Circuits? | Increase it |
| Why does Temperature affect Resistance in Electrical Circuits? | The more thermal energy, the more vibrations (kinetic energy) in the particles If particles are vibrating more, it's harder for the delocalised electrons to move through More collisions with electrons and ions |
| What is an Ammeter? | > Measures current flowing through the component > Can be placed anywhere in the main circuit > Must be placed in series with the component - placing it in parallel can cause short circuits |
| What is a Voltmeter? | > Measures potential difference across the component > Must be placed in parallel with the component to be tested |
| What does a Current-Potential Difference Graph look like for a Fixed Resistor? | |
| What does a Current-Potential Difference Graph look like for a Filament Lamp? | |
| What does a Current-Potential Difference Graph look like for a Diode? |
Image:
Diode (binary/octet-stream)
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| How would you setup a Test Circuit to Investigate how Potential Difference Changes with Current? | |
| What is the Right-Hand Thumb Rule? | do a thumbs up to the exam paper and it'll give you good luck, hopefully |
| What is the Motor Effect? | > A current-carrying conductor (e.g. a wire) in between magnetic poles cause a force on the wire > The two magnetic fields (from the magnet and the conductor) interact > The conductor exerts an equal and opposite force on the magnet |
| What Equation Links the Magnetic Flux Density, Length of the Conductor, Force, and the Current Through the Conductor? | Force (N) = Magnetic Flux Density × Current × Length F = B × I × l |
| What is Fleming's Left-Hand Rule? | |
| How do Motors Work? | > Forces act on two side arms of a wire carrying a current, which creates its own force as well > Forces act in opposite directions, so the wire rotates > Split-ring commutator swap the contacts every half turn to ensure the motor rotates in the same direction > Direction can be reversed by swapping the polarity of the DC supply or swapping the magnetic poles |
| What is Electromagnetic Induction? | > Electrical conductor (a coil of wire) and a magnetic field move relative to eachother > Moving a magnet into a coil of wire induces a potential difference and therefore current > The energy of the current isn't created from nothing, because that's physically impossible; the bottom of the conductor will become magnetised as well, repelling whichever pole of the magnet is going in. The work done going against the repulsion of the magnet causes the energy |
| What are the 3 Factors that Affect the Current Produced via Electromagnetic Induction? | An increase in these increase the size of the induced voltage: 1. Speed of magnet moving 2. Strength of magnetic field 3. Turns in the coil of wire |
| What are Transformers and How do they Work? | > Use electromagnetic induction > Change the size of the potential difference of a supplied alternating current > Two coils: primary and secondary, joined with an iron core (the coils aren't connected directly) > The AC produces an alternating magnetic field in the iron core > Magnetic field in the core also alternates > The changing magnetic field begins to induce a potential difference, and therefore a current in the secondary coil |
| What's the Difference between Step-Up and Step-Down Transformers? | > Step-Up: Increase the voltage, fewer turns on the primary coil > Step-Down: Decrease the voltage, more turns on the primary coil |
| What Equation Links the Input Voltage, Output Voltage, and Number of Turns on the Primary and Secondary Coil? | Input Voltage ÷ Output Voltage = Number of Primary Turns ÷ Number of Secondary Turns Vₚ ÷ Vₛ = Nₚ ÷ Nₛ |
| What Equation Links the Voltage and Current on both Primary and Secondary Coils in Transformers? | Voltage Primary Coil × Current Primary Coil = Voltage Secondary Coil × Current Secondary Coil Vₚ × Iₚ = Vₛ × Iₛ (assuming 100% efficiency) |
| How are Transformers Used in the National Grid? | > National grid uses AC current > Has to transfer a high power of energy > High current causes wasted energy in thermal energy / increased resistance > High voltage and low resistance reduces the power lost > Step-Up Transformers are used to boost the voltage high (up to 400,000V), which decreases the current (P = IV) > Step-Down Transformers reduce the current back to the usual 230V |
| What is Pressure Caused by? | > Particles in a gas move about at high speeds > Collisions with the container causes forces to be exerted at right angles to the surface > Force exerted creates pressure |
| How does Pressure Change due to the Volume and Why? | > Increasing the volume means the particles are more spread out, colliding with the container less often, decreasing pressure > Visa-versa for decrease of volume, pressure increases |
| What Equation Links the Pressure (1 and 2) at a Different Volume? | P₁ × V₁ = P₂ × V₂ |
| Why does the Volume of Elastic Containers (e.g. a balloon) Stay Constant even with Pressure? | > Pressure of the gas, inside the container, colliding, creating a force outwards is EQUAL to the atmospheric pressure, from the air, pushing inwards > Changing the external or internal pressure on the container can change the volume of the gas |
| What is Elastic and Inelastic Distortion? | > Elastic: can go back to original shape and length > Inelastic: object doesn't return to original shape, it has gone past the elastic limit |
| What Equation Links the Applied Force, Spring Constant, and Extension of a Spring? | Applied Force (N) = Spring Constant (N/m) × Extension (m) F = kx |
| Describe the Apparatus Used to Investigate the Spring Constant? | |
| Describe the Method Used in THE Spring Practical? | > Measure the natural / default length of the spring (when no load is applied) with a ruler clamped to the stand > Add a mass to the spring, allowing it to come to rest > Measure the new length according to the mass and calculate the extension > Repeat until the spring breaks or something idk |
| What can be done to Improve THE Spring Practical? | > Repeat for reliability > Use lower masses for more data points (to increase reliability and accuracy of graph plotted) > Avoid parallax errors by reading the ruler from eye level > Use a "Vernier scale" for more accurate measurement IF the spring is particularly small |
| hopefully that's it | i bet you L O V E electromagnetic induction... it's delicious :) |
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