Revision Quesrions Markscheme Flashcards
(16 cards)
Explain how rotation is caused in the motor.
- A split - ring commutator ensures the current is flowing in the right direction and changes every half turn (180°)
- flow of current creates a magnetic field
- opposite sides of the coil experience forces in opposite directions
Explain Flemings left-hand rule.
Thumb - force
Index/first finger - magnetic field
Middle/second finger - current
A teacher places 3 metal foil containers on top of the dome of the Van de Graaff generator. When it’s turned on, the foil containers fly off the dome one by one. Explain why this happens and use charge in your answer.
Charge is transferred
Charge is distributed across the dome or containers
Containers have same charges so they repel OR that electrons repel so charges on a container repel those charges (electrons)
“The supply voltage must not exceed 1V”. Why
Current increases so resistance of diode decreases (inverse proportion)
For a filament lamp, what is the graph of current against potential difference
It’s a steep curve that gradually flattens out.
As filament gets hotter, resistance increases, Ohms law says V=IR, which gives a straight line only if resistance is constant.
Why is resultant force 0
Forces are equal
Hookes law equation
F =kx
Force = spring constant x extension
Explain how the cork on water experiment shows that the wave travels but not the water.
The cork moves up and down and the waves move across the tray.
Period formula
T=1/f
Frequency formula
F=1/T
Wavelength formula
Speed/frequency
An object with the what specific heat capacity with the same mass will have the greatest temp rise?
The object with the lowest specific heat capacity
An aerosol canister should not be exposed to high temperatures. Explain why.
As temperature increases, the speed of particles increase, and kinetic energy of particles increase. Therefore particles collide more frequently.
Use the growths to describe the properties of Spring A and Spring B.
B shows plastic behaviour and B shows elastic behaviour.
A obeys Hookes law and so does B but in small forces only.
A is stiffer but plastic and b is more flexible but plastic.
A student rubs the plastic rod with a cloth and gains a positive charge. She holds the positively charged plastic rod above her head. Explain why the hairs on her head stand up. (3 marks)
The electrons in the hair move to the top of the hair, becoming negatively charged. So then are attracted to the protons on the rod, because opposite poles attract.
The student repeats the experiment with a metal rod and her hair doesn’t stand on end. Explain why.
Metal is a conductor (charges flow to earth)
