Mistakes Flashcards
Explain why particles moving in a circle do not change speed despite the force acting on them?
The force is acting towards the centre of the circle, therefore it is at right angles to the velocity, so the speed doesn’t change
Define electromotive force?
The energy transferred from one form of energy to electrical energy per unit charge
Define magnetic flux?
The product of the flux density and the area NORMAL TO THE FIELD
Explain how a simple transformer induces an emf in the secondary coil from an alternating voltage in the primary coil?
The AV produces a changing magnetic flux in the coil
The iron core links this magnetic flux to the secondary coils
The changing magnetic flux through the secondary coils induces an emf in the secondary coils
What happens to a ratio of two exponentially decreasing graphs over time?
It stays the same
What assumption is made when estimating density of a nucleus?
That the nucleons are tightly packed
Main reason it’s difficult to predict the future of the universe?
Existence of dark matter
Turn hubble constant:
65kms^-1Mpc^-1
To s^-1
(65x1000)/(3.1x10^22)
= 2.1x10^-18
Reason for using non invasive techniques in medical diagnosis?
Less chance of infection
Good moderator material?
Graphite
Explain why momentum can’t be worked out for very fast moving objects/electrons by dividing by the mass?
At high speeds the mass of the electron is greater than its rest mass
2 quantities conserved in beta decay?
Total mass and energy
Charge
How to calculate the max wavelength of X-Ray’s that can produce and electron positron pair?
E = hc/lambda
E = mc^2
Equate
Define activity?
The rate of decay of nuclei
State two properties of X-Ray PHOTONS?
Travel at 3x10^8ms^-1 IN A VACUUM
Highly ionising
