Electric Circuits Answers

What is meant by saying that a substance is “elastic”? A vertical brass rod of circular section is loaded placing a 5 kg weight on top of it if its length is 50 cm, its radius of cross-section 1 cm, and the Young’s modulus of the material 3.5 x 10^10 Nm-2. Find (a) the contraction of the rod (b) the energy stored in it.

If Young’s modulus for steel is 20.0 x 10^11 Nm^-2, calculate the work done in stretching a steel wire 100 cm in length and of cross-sectional area 0.03 cm^2 when a load of 100 N is slowly applied without the elastic limit being reached.

In an experiment to measure Young’s modulus for steel, a wire is suspended vertically and loaded at the free end. In such an experiment, (a) why is the wire long and thin (b) why is a second steel wire suspende adjacent to the first? Sketch the graph you will expect to obtain in such an experiment showing the relation between the applied load and the extension of the wire. Show how it is possible to use the graph to determine (a) Young’s modulus for the wire(b) the work done in stretching the wire.

A wire of radius 0.2 mm is extended by 0.1% of its length when it supports a load of 1 kg. Calculate Young’s modulus for the material of the wire.’

What do you understand by Hooke’s law of elasticity? Describe an experiment to determine Young’s modulus of an elastic material.

A copper wire AB is fused at one end B to an iron wire BC. The diameter of the copper wire is 0.50 mm and that of the iron wire is 2.50 mm. The compound wire is stretched so that its length increases by a total amount of 0.1 cm. (AB=9.00 x 10^2mm and BC = 4.50 x 10^2mm) Calculate; (a) The ratio of the extension of the copper wire to that of the iron wire (b) The tension applied to the compound wire (NB: Young modulus of copper = 1.3 x 10^11 Pa while that of iron = 2.0 x 10^11 Pa)

Distinguish between Young’s modulus and elastic constant

The rubber cord of a catapult has a cross-sectional area of 1.0 mm^2 and a total upstretched length 10.0 cm. It is stretched to a 120 cm and then released to project a missile of mass 50 g. From energy consideration or otherwise, calculate the velocity of projection, taking Young’s modulus for the rubber as 50 x 108 Nm^-2. State the assumptions made in your calculation.

Explain the terms stress, strain, modulus of elasticity and elastic limit. Derive an expression in terms of tensile force and extension for the energy stored in a stretched rubber cord which obeys Hooke’s law.

What is meant by (i) elastic limit (ii) Hooke;s law (iii) yield point (iv) perfectly elastic? Draw sketches of stress against strain to illustrate your answers.