Questions I got wrong Flashcards
(26 cards)
What form is the energy fromt decay released as?
Kinetic energy and gamma radiation
What alpha scattering experiment infers
-nucleus is charged
-the mass is concetrated in nucleus
Explain why ultrasound used in medical diagnosis is emited in pulses
-so tranducer can recieve extended pulse of reflected ultrasound waves
By reference to what is meant by the thermodynamic scale of temperature, comment on your answer in (i)
thermodynamic scale doesn’t depend on the property of a substance so change in resistance with temperture is non-linear
Explain why when a small test charge is moved from point P to point Q, the net work done is zero
Potential at P is the same as potential at Q
Work done =qV
V=0 so zero work done
Explain why initially, the electrons do not travel in straight lines across the slice from side SR to side PQ
-force on electron due to magnetic field
-force on electron normal to magnetic field and direction of electrons
Explain what is meant by the root-mean-square value of an alternating voltage
-the value of steady/constant voltage
-that produces same power as the alternating voltage
State what is meant by the work function energy of a metal
-photon energy to remove electron
-energy to remove elctron from surface
Explain the principles of the detection of ultrasound waves used in medical diagnosis
-piezo electric crystal
-ultrasound makes crystal vibrate
-vibration produces alternating pd across crystal
Explain why an aluminium filter may be placed in the X-ray beam when producing an X-ray image of a patient
-filter absorbs low energy X-rays
-X-ray beam contains many wavelengths
-so low energy x-rays are not absorbed in the body
Three pieces of evidence provided by the photoelctric effect for a particulate nature of electromagnetic radiation
-instantaneous emission of electrons
-energy of emitted electrons depends on frequency
-energy of emitted electrons does not depend on intensity
random
time at which a nucleus will decay canoot be predicted
Spontaneous
decay not affected by environmental factors
2 different functions of capacitors
-storage of charge
-blocks dircet current
Would the same power be dissapated in a 1 ohm resistor connected to each power supply?
Only if the r.m.s voltages are the same
describe the e.m.f of a battery
energy transferred from chemical to electrical per unit charge
describe the p.d across a resistor
energy transferred from electric to thermal per unit charge
Why is it impossible for the magnitdue of a charge to be 8.0x10^-20C
because it is a smaller charge than a fundamental particle
Why the gravitational potential near an isolated mass is always negative
-gravitational force is attractive
-gravitational potential at infinity is zero
-decrease in potential energy as masses approach
Why an alternating current gives rise to a heating effect in a resistor
-heating effect in a resistor r proportional to c squared
-square value of alternating current is always positive
-so hating effect occurs
Use faraday’s law to explain why the current in the primary coil is not in phase with e.m.f induced in the secondary coil
-flux in core is in phase with the current in the primary coil
-induced e.m.f in secondary becasue coil cut the flux
-flux and rate of change of flux are not in phase
the spectrum of the light emerging from the gas cloud is found to contain a number of dark lines
Explain why these dark lines occur
photon ‘absorbed’ by electron
photon has energy equal to difference in energy of two energy levels
Electron de-excites emitting photon in any direction
Why gravitational potential is negative at a point
At infinity the gravitational potential is 0
Gravitational force is attractive
Work is done on two mass in moving them apart
Why the potential energy of ideal gases is 0
No intermolecular forces
So potential energy is zero
