Describe how the force on the pedal causes a moment around the rear axle
The force on the peddle causes a moment about the rear axle, which causes a force on the chain
Explain how protective pads help to reduce the injury when the players collide
- Protective pads increase the time taken to stop during the collison
- So the rate of momentum decreases
- reducing the force
What is inertia
The tenency of an object to continue in its state of rest or motion
person wanted to find wave speed of water waves but didnt measure the wavelength how would they work it out.
- Teacher measure a set distance in the ripple tank
- Count how long it takes for waves to travel set distance.
- Divide distance by speed
The ray of light from the ray box should be as narrow as possible, explain why
- Harder to judge where the centre of a wider ray is, causing larger uncertaincy in the measurements
How does ariel transmitons occur
- Alternating current induced in eletrical circuit
- With the same frequency as the radio wave
How does redshift support big bang
- Furthest galixes moving the fastest
- Suggesting the unvierse expanded from one very small region
All units
The
Great
Mighty
King
Explain how a moving coil loudspeaker produces a sound wave
- Current creates a magnetic field around the coil
- Which interacts with the pernament magnet
- Producing a resultant force on the coil/cone causing it to move
- When the dirrection of the current reverses the dirrection of the force reverses producing a sound wave
Explain why thinking distance effects stopping distance
- Stopping distance includes braking distance + thinking distance
- Additonal time is takne for breaks to be pressed
- Increase in stopping distance
Explain why the temperature of the breaks increases as they are used
- Work is done due to friction in the breaks
- Causing an increase in the internal energy
What is meant by a closed system
- total amount of energy remains constant in system
Explain how the effect of the earths gravitatinol force effects the motion of a telliscope
- Gravitational force causes telliscope to accelerate towards earth
- This changes dirrection of motion
- This changes velocity of hubble teliscope
Name for reflection on a smooth surface
scapular reflection
Name for reflection on a unsmoth surface
diffuse
Explain in terms of wave fronts why refraction happens at the boundry between glass
- different parts of the wavefront
enter the glass at different times - the velocity / speed (of light) is
less in glass - (so) one part of the wave front
changes speed before other
parts
A dynomo is used to generate an eletric current
The coil is rotated
Explain why a direct current is induced in the coil
- The coil moves through magnetic fields cutting magnetic lines
- A potential difference is induced across the coil
- There is a complete circut so current is inuced in coil
- Each half turn the two ends of the coil swap from one brush to the other
- So the current of the induced current does not alternate each half turn
The lamp is disconnected from the dynamo, explain why the dynamo became easier to turn
- After disconnected there is no induced current
- So no magnetic feild produced around coil
- To oppose movement of the coil
A transformer can be adjusted to have different number of turns on the secondary coil, suggest why.
- To vary the potential difference
- So that you dont need a diferent generator for each different device
The handle the alternator is turned, causing the coil to rotate
Explain why an alternating current is induced int the coil
- The coil moves through the magnetic feild (cutting through lines)
- Potential difference indiced across coil
- Complete circuit so current is induced
- Every half turn the the potential differnce reverses dirrections
- So every half turn current changes dirrection
How does a dynamo generate electricity?
A dynamo uses a rotating coil or magnet in a magnetic field.
It produces a direct current (DC).
As the coil spins, it cuts through magnetic field lines, inducing a current.
A commutator switches the direction so the output stays as DC.
How does an alternator generate electricity?
An alternator also uses a rotating magnet or coil in a magnetic field.
It produces an alternating current (AC).
As the magnet spins, the direction of the induced current reverses every half-turn.
It uses slip rings instead of a commutator, so the current alternates smoothly.
Describe how a generator works to produce electricity.
Coil or magnet spins in magnetic field
Magnetic field lines are cut
A current is induced in the coil
In a dynamo: commutator produces direct current (DC)
In an alternator: slip rings produce alternating current (AC)
Current is transferred to the circuit
“Explain how a dynamo produces a direct current.”
Coil rotates in magnetic field
Magnetic field lines are cut
Induced current created
Commutator switches current direction every half turn → net current flows in same direction
Produces DC output
