Electromagnetism

A question from magnetism

From the graph identify the types of magnetic materials A,B and hence give an example for each one of them.

Asked Vikas.

Doubts and Questions from AC

Why there are Sine functions in Physics?

Why are sine functions used in some of the equations in physics?
For example,in the expression for instantaneous emf induced in a rotating conductor placed in an uniform magnetic field which is given by
E=B*L*V*sin(theta)
where,
B is the strength of the magnetic field,L is the length of the conductor and (theta) is the angle between the direction of motion of the conductor and the magnetic field,and here,my question is why do we use sine function in this expression?what is its need?

Answer:

The function sin (theta) in a right angled triangle = opp. side /Hypotenuse

When we have to take a component perpendicular to another, we take the sine function.

(the answer will be updated with more information soosn)

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• Why is the force on a wire NOT carrying current is zero when kept in a magnetic field?

Transformers

A hypothetical ideal transformer considered as a circuit element, consisting of N P turns in the primary winding, and N S in the secondary. Electrical power supplied to the primary circuit is delivered to the load in secondary circuit by means of mutual induction. The time-varying magnetic flux in the core generates an electromagnetic force over each of the windings. The voltage and current relationships are shown below. (Photo credit: Wikipedia)

Please explain what is transformer and tell what is the reason behind the working of transformer that it reduces potenial when current is high and increases potential when current is low?

Explain widely and deeply with concepts.

Answer:

Transformer is a device based on mutual inductance and is used to change the voltage of alternating (or varying) current. There are two types of transformers – stepup and stepdown.

A step-up transformer increases the voltage as the step-down transformer decreases the ac voltage.

When a transformer changes the alternating voltage, it is not adding any power, it only transforms the voltage.

As power is the product of voltage and current, as voltage increases, the current decreases. (and vice versa)

The following links will help you understand transformers in great detail.

• http://www.physlink.com/education/askexperts/ae427.cfm
• http://en.wikipedia.org/wiki/Transformer
• http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/transf.html
• http://www.nuffieldfoundation.org/practical-physics/explaining-how-transformer-works