# Why is the value of EMF generated by a generator not zero at t = 0 s?

• songoku
In summary, the value of EMF generated by a generator is not zero at t = 0 s because there is no change in magnetic flux. It is calculated using Faraday's law of induction and can be negative if the magnetic flux decreases. The speed of the generator directly affects the value of EMF generated, with a higher speed resulting in a higher value. However, the value of EMF generated decreases over time due to factors such as internal resistance and external load.
songoku
Homework Statement
This is not homework.

Let say coil of generator is in horizontal position (i.e. the direction of magnetic field of the magnet is perpendicular to the normal vector of the plane of the coil). The coil is then rotated so emf will be induced on the coil.

If I draw the graph of Φ (magnetic flux) against time, the shape will be like sin wave and if I draw the graph of emf against time, the graph will be like negative cosine wave so it means that the starting point of graph of emf against time will a certain negative value (let say -5 V).
Relevant Equations
ε = - N . dΦ / dt
Does this mean that initially there will be emf induced on the coil at t = 0 s?

Initially, at t = 0 s, the coil has not been rotated yet so based on Faraday's Law, there won't be any change in magnetic flux so why the value of emf is not zero at t = 0 s?

Thanks

songoku said:
at t = 0 s, the coil has not been rotated yet
No, but it is rotating. The emf is created by movement, not position.

Delta2 and songoku
haruspex said:
No, but it is rotating. The emf is created by movement, not position.
Thank you very much haruspex

## 1. Why is the value of EMF generated by a generator not zero at t = 0 s?

The value of EMF (electromotive force) generated by a generator is not zero at t = 0 s because there is still a change in magnetic flux occurring at that moment. This change in flux creates an induced electric field, which in turn generates an EMF.

## 2. What causes the change in magnetic flux at t = 0 s?

The change in magnetic flux at t = 0 s is caused by the rotation of the generator's rotor, which creates a changing magnetic field. This changing field then passes through the stationary coils of the generator, inducing a current and generating an EMF.

## 3. Does the value of EMF at t = 0 s affect the overall output of the generator?

Yes, the value of EMF at t = 0 s is crucial for the overall output of the generator. It determines the initial current flow in the circuit, which then affects the overall power output of the generator.

## 4. Can the value of EMF at t = 0 s be reduced or eliminated?

The value of EMF at t = 0 s cannot be completely eliminated, as it is a natural result of the changing magnetic flux in the generator. However, it can be reduced by using specialized circuitry or by adjusting the design of the generator.

## 5. Is the value of EMF at t = 0 s the same for all types of generators?

No, the value of EMF at t = 0 s can vary depending on the type of generator. Different designs and sizes of generators can produce different levels of initial EMF at t = 0 s, which can also affect their overall performance.

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