Edexcel A-Level Physics 6 Mark Questions Paper 1

Explain how a cyclotron produces a high-energy proton beam

IC1 - There is an alternating p.d./electric field

IC2 - p.d./electric field accelerates protons between dees

IC3 - Magnetic field perpendicular to plane of dees

IC4 - Proton path curved by magnetic field

IC5 - As velocity of protons increases the radius of path in dees increases

IC6 - The time for which a proton is in a dee OR the frequency of p.d./electric field remains constant

In a simple electric motor, explain why the current rises to a maximum then decreases. (Your answer should include a reference to Faraday and Lenz's laws).

IC1 - Maximum/initial current is equal to battery emf divided by R

IC2 - Coil rotates

IC3 - Movement of coil changes the magnetic flux linkage

IC4 - This induces an emf according to Faraday's law

IC5 - This opposes the original emf according to Lenz's Law

IC6 - The faster the coil rotates the the smaller the current, so current decreases

'The frictional force between an object and a surface is directly proportional to the mass of an object'. In an experiment a student tapped a 2p coin to it travelled s metres with initial velocity u. She swapped it with a 1p coin and repeated the process. She suggested u is directly proportional to the square root of s and is independent of the mass of the coin. Discuss the validity of this statement.

1 - Use of v^2 = u^2 + 2as

2 - v = 0 so u = root 2as

3 - a is deceleration caused by friction

4 - F = ma where F is friction

5 - If F is proportional to m then a must be constant

6 - So acceleration is the same for the 2p and 1p coin so the statement is correct

Muons are produced at a height of 10km in the atmosphere. The velocity of the muons is 0.99c. The average lifetime of muons is normally 2.2 microseconds and yet muons produced in the supper atmosphere are found in significant numbers at sea level. Discuss this apparent anomaly.

IC1 - Uses velocity = distance/time

IC2 - Calculates a time 3x10^-5s

IC3 - Compares with 2.2x10^-6s which is 15 times smaller

IC4 - Identifies relativistic effects as velocity close to c

IC5 - Time dilation means time between events is longer

IC6 - So muon lifetime increases

Hybrid electric vehicles (HEV) use the same device both as a generator to charge the car battery and as an electric motor to support the propulsion system. Describe how the device can be used as both a generator and an electric motor.

Generator:

IC1 - Coil has to be rotated

IC2 - rate of change of magnetic flux linkage

IC3 - Induces an emf

Motor:

IC4 - current provided to coil

IC5 - Force on sides of coil that are perpendicular to magnetic field

IC6 - Forces provide a moment so coil rotates

Explain how observations and measurements from a bubble chamber photograph can be used to establish information about a particle.

IC1 - State charge of particle

IC2 - Evidence in track left by particle

IC3 - radius of curvature gives momentum of particle

IC4 - Because of B=qvr

IC5 - laws of conservation of momentum can be applied

IC6 - determining momentum/energy of the particle

Explain how an electron is accelerated in a linac.

IC1 - Set of metal tubes in a line

IC2 - Electrons accelerated by electric field/p.d.

IC3 - Acceleration takes place in the gaps between tubes

IC4 - Adjacent tubes connected to opposite terminals of a power supply or are opposite charge

IC5 - power supply/p.d./electric field is alternating

IC6 - time period/time spent in each tube must be constant so as electrons travel faster the tubes and gaps must get longer

A split ring consists of two semi‑circular sections that are attached to a coil. Two brushes, made of carbon, rub against and make electrical contact with the split ring. Describe how this arrangement can lead to the coil rotating.

IC1 - The current flows in the coil in a certain direction

IC2 - There is a force due to current within a magnetic field

IC3 - Direction of force can be determined using F=BIl

IC4 - The moment of force round the axis causes rotation

IC5 - as the coil moves through half a turn the split ring ensures the current switches direction

IC6 - This results in the coil continuing to rotate in the same direction

In an experiment, negatively charged oil drops are allowed to fall between two parallel metal plates. A potential difference (p.d.) is applied across the plates. When the p.d. is 0V the oil drop accelerates to terminal velocity. The p.d. is increased. It is observed that at a particular p.d. 'V' the oil drop stops falling and remains stationary between the plates. Explain the motion of the oil drop in terms of the forces acting on it as the p.d. is increased from 0 to 'V'.

IC1 - At terminal velocity the forces on the drop are balanced so weight = drag

IC2 - The p.d. creates an electrostatic force acting upwards on the drop

IC3 - The electrostatic force increases as p.d. increases

IC4 - The net upwards force causes the drop to have a negative acceleration

IC5 - As speed decreases the drag decreases

IC6 - The drop remains stationary when forces are balanced and and weight = electrostatic force

An electric toothbrush charger contains a coil wrapped around an iron core. The coil is plugged into the mains a.c. supply. The toothbrush also contains a coil that sits around the iron core when the toothbrush is placed on the charger to recharge the battery of the toothbrush. The coil is connected to a circuit inside the toothbrush with a battery and diode. Describe how the charger is able to charge the low-voltage battery.

IC1 - The supply creates a changing magnetic field in the iron core

IC2 - Rate of change of flux in toothbrush coil is equal to the rate of change of flux in charger coil

IC3 - The changing flux linkage in the coil of the toothbrush induces an emf according to Faraday's Law

IC4 - E = -N/dt so to step down down emf there must be fewer turns in the toothbrush coil

IC5 - The emf in the toothbrush coil must be larger than the toothbrush battery

IC6 - Diode is included so the battery in the toothbrush is not discharged by the alternating emf