P2 summary.
- Created by: Abbs11_
- Created on: 02-05-16 15:09
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- PHYSICS 2.
- Static and current electricity.
- To stop electrostatic charge building up we can connect the charged object to the ground - this is called earthing.
- Earthing provides an easy route for the static charges to travel into the ground.
- This means no charge can build up to give you a shock or make up a spark.
- Earthing provides an easy route for the static charges to travel into the ground.
- Current is the rate of flow of charge around a circuit.
- In the metal wires of a circuit, this charge is carried by electrons.
- Charge (Q) = current (I) x time (T)
- In the metal wires of a circuit, this charge is carried by electrons.
- To stop electrostatic charge building up we can connect the charged object to the ground - this is called earthing.
- Controlling and using electric current.
- Current - the rate of flow of charge around the circuit.
- Unit = ampere, A
- Voltage - the driving force that pushes the current round.
- Unit = volt, v. can also be called potential difference.
- Potential difference (V) = current (I) x resistance (R)
- Unit = volt, v. can also be called potential difference.
- Resistance - is anything in the circuit which slows down the flow.
- Unit = ohm
- If you increase the resistance, then less current will flow.
- If you increase the voltage then more current will flow.
- Electrical power (P) = potential difference (V) x current (I)
- Energy transferred (E) = current (I) x potential difference (V) x time (T)
- Light dependant resistor (LDR) changes its resistance depending on how much light there is.
- In bright light, the resistance falls.
- In darkness, the resistance is highest.
- Thermistor (temp dependant resistor.)
- like an LDR but its resistance depends on temperature.
- In hot conditions the resistance drops.
- In cold conditions, the resistance goes up.
- like an LDR but its resistance depends on temperature.
- Current - the rate of flow of charge around the circuit.
- Motion and forces.
- Speed - how fast you're going,
- Speed (S) = distance (D) / time (T)
- Velocity - how fast in a specific direction.
- Acceleration - is how quickly the velocity is changing.
- This could be change in speed.
- Or change in direction.
- Or both.
- Acceleration (A) = change in velocity (V-u) / time taken (T)
- When two forces interact they exert a force on each other.
- If object A exerts a force on object B then object B exerts the exact opposite force on object A.
- Resultant force.
- Force (F) = mass (M) acceleration (A)
- The bigger the resultant force, the greater the acceleration or deceleration.
- The bigger the mass of the object, the smaller the acceleration.
- To get a big mass to accelerate as fast as a small mass it needs a bigger resultant force.
- Speed - how fast you're going,
- Momentum, energy, work and power.
- The greater the mass of an object and the greater its velocity the more momentum the object has.
- Momentum(Kg m/s) = Mass (Kg) x velocity ( m/s)
- When a force acts on an object, it causes a change in momentum.
- Force (N) = change in momentum(Kg m/s) / time (S)
- When a force moves on an object, energy is transferred and work is done.
- Work done (E) = Force (F) x distance moved in the direction of the force (D)
- Power is something transfers a lot of energy in a short space of time.
- Power (P) = work done (E) / time taken (T)
- Energy can never be created nor destroyed - only transferred from one form to another.
- Energy is only useful when its transferred from one form to another.
- The greater the mass of an object and the greater its velocity the more momentum the object has.
- Nuclear fission and nuclear fusion.
- Ionisation.
- Atoms can gain or lose electrons. When an atom (with no overall charge) loses or gains an electron it is turned into an ion (which is charged).
- Nuclear fission.
- A type of nuclear reaction that is used to release energy from uranium or plutonium atoms.
- Nuclear Fusion.
- The opposite to nuclear fission.
- Two light nuclei collide at high speed and join to create a larger nucleu
- More energy is created than fission.
- Only happens at high temperatures and pressure.
- Ionisation.
- Using radioactive materials.
- Background radiation - is low level radiation thats around us all the time.
- The half life of a radioactive isotope is the time taken for half of the undecayed nuclei to decay.
- Half-life.
- A short half life means the activity falls quickly because lots of the nuclei decay quickly.
- A long half life means the activity falls more slowly because most of the nuclei don't decay for a long time.
- Half-life.
- Uses for: Alpha, Beta, Gamma.
- Alpha.
- Used in smoke alarms.
- Beta.
- Thickness control in paper mills.
- Alpha.
- Pros and cons of nuclear power.
- Dangerous.Cant be disposed of safely.
- Very reliable. Not as risky as perceived.
- Doesn't release gases such as sulphur dioxide - so clean source of energy
- Huge amounts of energy created from small amount of nuclear material.
- Cheap - readily available.
- However cost of the nuclear power plant is very expensive.
- Static and current electricity.
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