Physics Paper 2 Marking Scheme
KCSE CLUSTER TESTS 27
Physics Paper 2
SECTION A (60 Marks)
Answer ALL the questions in this section
2 marks
On earthing negative charges are repelled to the ground. When the rod is withdrawn, the leaf if left with a net positive charge
2 marks
Manganese (iv )oxide is a slow depolarizer and polarization occurs with a large current, on resting, the depolarization returns the p.d of the dry cell.
2 marks
Heating makes the depoles to be excited to a high energy state where they swing freely. As they resettle the depoles will easily align themselves with the earth’s magnetic field
2 marks
Image is virtual/ erect/magnified
1 marks
Soft Iron armature should be easily magnetized and demagnetized. It concentrates the magnetic field inside the core to increase the magnetic strength.
2 marks
3 marks
2 marks
2 marks
2 marks
A narrow beam of microwaves is sent out in the short pulses from the radar. Distant objects in the path of the beam reflect part of the waves back. The reflected waves give the direction and the distance of the reflecting object
2 marks
1 marks
2 marks
The electrons are accelerated to very high velocities by the high p.d between the cathode and the anode and part of their kinetic energy is converted to X-rays.
2 marks
SECTION B (20 Marks)
Answer all the questions in this section.
7 marks
a) Lenz’s law: it states that the direction of the induced e.m.f is such that induced current which it causes to flow produces a magnetic effect that opposes the change producing it.
b) i) – The galvanometer gives a deflection when the magnet is moving towards the coil.
- The magnetic flux linking the coil is increasing and an e.m.f and hence current is induced in the coil.
ii) Work done in moving the N-pole against an opposing force.
c) Eddy current – by laminating the iron core.
Hysteresis - by having the core made of soft iron (soft magnetic material)
Heating - having the nails made of thick copper wires
ii) The cells in the secondary, because the current is much smaller.
16 marks
a) X – Gamma rays
Z – Beta particles. Gamma rays are not deflected by magnetic field. Beta rays/particles are light and are deflected most.
b) i) Shown on graph half – life 2 hours.
ii) This is because of background radiation which enables the counter to record some count
c) Alpha particles are massive and have a low penetrating power and will be stopped by the Aluminum foil.
15 marks
. a) – Area of overlap
- Distance of separation
- Nature of the dielectric.
8 marks
a) Real image is formed when rays of light are brought to a focus/meet while virtual image is formed when rays of light appear to meet but do not actually meet.
Image is 60cm from the lens and on same side as the object.
12 marks