# Shared Flashcard Set

## Details

Edexcel module 12 higher
GCSE
39
Physics
Not Applicable
05/13/2007

Term
 What is the electrical Power equation?
Definition
 Power = Voltage x CurrentP=VI
Term
 What is the relationship between pressure and volume in a closed system?
Definition
 P1V1=P2V2
Term
 What is the relationship between power, energy and time?
Definition
 Energy(joules)=Power(watts)xtime(seconds)
Term
 What is the energy transferred by an electric fire connected to a 230V mains which carries 5A and which is on for 20min?
Definition
 Power = Volts x Amps= 230 x 5 =1150WEnergy = power x time(in seconds)= 1150 x 1200=1380000J = 1.38MJ
Term
 How can an insulator be charged by friction?
Definition
 By rubbing it with a cloth.
Term
 What are the units of frequency?
Definition
 Hertz (Hz)
Term
 What is the unit of speed?
Definition
 metres/second (m/s)
Term
 What is the unit of wavelength?
Definition
 metre (m)
Term
 Recall the wave equation
Definition
 wave speed(m/s) = frequency(Hz)x wavelength(m)
Term
 What is the relationship between voltage and number of turns on a transformer?
Definition
 V primary/Vsecondary=Turns pimary/turns secondary
Term
 How are step up transformers used in the electrical grid?
Definition
 Voltage is stepped up at the power generating station before distribution.
Term
 When are step down transformers used in the electricity grid?
Definition
 Before the voltage is supplied to consumers it is reduced to 230V from high voltages eg 400kV
Term
 What material is used for the core of a transformer?
Definition
 soft iron laminated
Term
 work out the frequency of a wave of length 2m travelling at 330m/s
Definition
 frequency=wavespeed/wavelength=330/2=165Hz
Term
Definition
 digital
Term
 Why is electricity transmitted at high voltages?
Definition
 this reduces the current required so reduces the energy lost due to heating effects
Term
 Why is electricity used in the home at low voltages?
Definition
 safer - less likely to cause death by electrocution
Term
 What is the voltage at the secondary of a transformer attached to a 230V supply if the primary coil has 500 turns and the secondary has 25 turns?
Definition
 V2= V1xT2/T1=230x25/500
Term
 Which of these are transmitted by waves? Matter, energy,information
Definition
 energy and information
Term
 A transformer is used to light a 3V bulb from a 24V supply. Is it a step up or step down transformer?Calculate the number of turns on the secondary if there are 400 turns on the primary.
Definition
 step downT2 = T1xV2/V1= 400x3/24= 50turns
Term
 A container of volume 1 litre contains a fixed mass of gas at 500N/m2. If the volume is reduced to 250cm3 what will be the new pressure of the gas?
Definition
 P2=P1xV1/V2=500x1/0.25=2000N/m2
Term
 What happens when waves pass through a narrow gap or past an edge?
Definition
 They are diffracted.
Term
 Which type of waves show diffraction effects?1. Sound2. Light3. Both sound and light
Definition
 3 Both sound and light.
Term
 What does Boyle's law state?
Definition
 The pressure of a fixed mass of gas is proportional to the volume of the gas.
Term
 How do the particles in a gas move?
Definition
 Randomly
Term
 How does a gas exert pressure?
Definition
 By random collisions of the gas particles with the walls of the container or other surfaces.
Term
 describe the relationship between the applied force and extension of an elastic object
Definition
 Extension is directly proportional to applied force (Hooke's law)
Term
 What is voltage?
Definition
 the energy transferred per unit charge passed ie a volt is a joule/coulomb
Term
 What happens to a current carrying wire in a magnetic field?
Definition
 A force is exerted upon it perpendicular to both the direction of the field and the direction of current flow
Term
 Describe how electrostatic charges interact.
Definition
 Like charges repel; unlike charges attract
Term
 What happens when an insulating material such as amber is rubbed with a cloth?
Definition
 It becomes charges due to the transfer of electrons.
Term
 Whcihc types of material are insultaors and which are conductors?
Definition
 metals are conductorsplastics, glass, wood and other non-metals are mainly insulators
Term
 Describe a situation in which build up of electrostatic charge may be dangerous.How is the danger reduced or eliminated?
Definition
 Refuelling an aircraft: friction of the fuel in the pipe leads to build up of charge between the aircraft and the ground. A discharge could cause fire/explosion.Earthing the aircraft by connecting it to the ground with a wire(Car body - after driving: again earth)(synthetic fabrics rubbing on car seat charge passenger)(lightning - use lightning conductor to leak charge to air)
Term
 What is an electric current?
Definition
 Current is the rate of flow of charge.It involves the flow of electrons in metals or ions in electrolytes.
Term
 What is the charge on an electron?
Definition
 negative
Term
 Some common salt is dissolved in water. A potential difference is applied to two electrodes placed in the salt solution. Explain what will happen.
Definition
 A current will flow as positively charged sodium ions are attracted to the cathode(negative electrode) where they collect electrons. At the same time negatively charged chloride ions are attracted to the anode(+ve electrode) where they release electrons.
Term
 How can the insulator solid lead bromide be made to conduct a current?
Definition
 Melt it so the lead and bromide ions can move to the electrodes.
Term
 What is total internal reflection and when does it occur?
Definition
 When a ray of light strikes a surface between two media at an angle such that all of the light is reflected back into the medium in which the light is travelling. This is called the critical angle
Term
 Describe how total internal reflection is used.
Definition
 1) cats eyes - light from headlight reflected back to car by prism shaped glass in cats eye2) in optical fibres - light ray strikes side of fibre and all is reflected along the fibre so no loss of energy occurs - eg in telephone cables, endoscopy etc
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