Mechanics - Simple pendulum - Experiment 5

The aim of this experiment is to find the ratio P defined in part (d) by using a simple pendulum.

Suspend the pendulum bob with its upper part of the string fixed on a retort clamp as shown in figure below. Make a knot Nat a distance of L =10cm from the bob B. While X is the distance between the point of suspension S to a knot N on the string

Set X=60cm and pull the bob aside at a small angle so that it can start swinging vertically

(a)  Record the time t for 30 oscillations of the pendulum bob

(b)  Repeat the above procedure for the values of X= 50, 40, .....  CONTINUE READING

Solution - Extra Explaining Questions - ELECTROMAGNETISM

ELECTROMAGNETISM

1. Explain why transformer are used to reduce the current passing through the transmission cables of the National Grid

[Show answer]

The transformer (Step –up) reduces the current passing through the transmission cables of the National Grid so as to reduce the energy wasted (Power Loss) by heating up the cables.

2.   Explain why transformer does not work using a d.c. supply. Why is an a.c. supply necessary to make a transformer work?

[Show answer]

According to Faraday Law of Electromagnetism that says “wherever there is change of magnetic flux (linking the coils) e.m.f is induced, so if the d.c is supplied to the primary coil of the transformer the magnetic field is constant (No change of magnetic flux). Then no potential difference (voltage) induced in the secondary coil.

3.  Explain why a bicycle lamp attached to the to the dynamo does not light when the.....  CONTINUE READING

FRICTION FORCE AT INCLINED PLANE

Consider the diagram below, a mass of body sliding down the incline plane

At constant speed a = 0m/s²

F_k = mgsinθ

R = mgcosθ

But:

Fk = μ_kR – make μ_k subject

μ_k = F_k/R

μ_k = mgsinθ/mgcosθ

μ_k = sinθ/cosθ

μ_k = Tanθ

Therefore, at constant speed coefficient of ..  CONTINUE READING

Cooling Effect of Evaporation

What is evaporation?

Evaporation is the gradual change of state from liquid to gas that occurs at the surface of the liquid

Evaporation occurs when particles escape from a liquid. This happen even when the temperature is lower than the boiling point.

Factors affecting evaporation

i.     Temperature

An increase of temperature increases the rate of evaporation

ii.    Surface area

A larger surface area allows more particles to leave the liquid hence the larger the surface area the higher rate of evaporation..  CONTINUE READING