# Mmmmmmmmmmmmmm

**Topics:**Transformer, Temperature, Alternating current

**Pages:**5 (1031 words)

**Published:**February 6, 2013

1. You are to spend no more than ½ hour on this question. In this question you will find the value of the resistance, R, of a heating element. The voltage, V, across the heating element is varied and the power, P, which is dissipated, is measured. (Note that R remains constant during the heating.) A graph of P against V is plotted on page 2. (a) Select 6 pairs of values of P and V from the graph and insert these along with corresponding values of V2 in Table 1 below. P (watts) V (volts) V2 (volts 2) Table 1 (b) (c) Plot a graph of P against V2 on the graph sheet. Find the slope, S, of the graph you have plotted. ……………………………………………………………………………………………… ……………………………………………………………………………………………… (4 marks) (d) The equation for the beating element is Use this equation and your value for R so as to find the resistance of the heating element. ……………………………………………………………………………………………… ……………………………………………………………………………………………… ……………………………………………………………………………………………… (3 marks) (e) Estimate the power, P,, which would be dissipated in the element if the applied voltage is 300 volts. ……………………………………………………………………………………………… ……………………………………………………………………………………………… (3 marks) (f) If 300 V were applied for 15 minutes, calculate the energy used in kWh. ……………………………………………………………………………………………… ……………………………………………………………………………………………… (3 marks) Total 30 marks Formatted by: ReThink Physics | www.rethinkphysics.blogspot.com

(8 marks)

(9 marks)

CXC CSEC Physics | Paper 02 | 2001

2. This question concerns the motion of a small jet plane. (a) The plane accelerates from rest along the runway at 3.4 m s -2. If it takes 18 seconds to take off, at what speed does it leave the ground? ……………………………………………………………………………………………… ……………………………………………………………………………………………… (3 marks) (b) State Newton's First and Third laws of motion. ……………………………………………………………………………………………… ……………………………………………………………………………………………… ……………………………………………………………………………………………… ……………………………………………………………………………………………… ……………………………………………………………………………………………… (4 marks) (c) Figure 1 shows the small jet plane flying at a constant speed and at a constant height.

(i)

In addition to the two forces shown on the diagram, two other forces, the weight and the thrust of the engines, act on the plane. On Figure 1, draw TO THE SAME SCALE, lines representing these other forces. (3 marks) The engines now emit exhaust gases at a higher rate. Explain how this causes the plane to accelerate. …………………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………………………… (2 marks) Formatted by: ReThink Physics | www.rethinkphysics.blogspot.com

(ii)

CXC CSEC Physics | Paper 02 | 2001

(iii) The plane now circles at a new constant speed. Figure 2 shows one view of the plane as it circles.

Explain how the 'banking' (tilting to the horizontal) of the plane allows the lift to maintain the plane's circular motion and its height. ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ………………………………………………………………………………………………………. ……………………………………………………………………………………………………… (3 marks) Total 15 marks

Formatted by: ReThink Physics | www.rethinkphysics.blogspot.com

CXC CSEC Physics | Paper 02 | 2001

3. (a) Draw a labelled diagram of a step-up transformer.

(b)

Table 2 lists the main sources of energy loss in a real transformer. Complete Table 2. Source of energy loss Method used to reduce Energy loss

1. Heating in coil wires 2. Eddy current losses in core 3. Magnetisation and demagnetisation of core 4. Imperfect flux linkage

Table 2 (4 marks) (c) Explain why alternating current (a.c.) is preferred to direct current (d.c.) for the transmission of electrical energy over long distances. ………………………………………………………………………………………………………. ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ………………………………………………………………………………………………………. (3 marks) Formatted by: ReThink Physics | www.rethinkphysics.blogspot.com

CXC CSEC Physics | Paper 02 | 2001

(d) (i) A...

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