What Causes a Transformer with 240V Input to Have No Output?

[Ry122]

Just need help with 2 questions
If someone can just give me the formula for the second question i should be right.

Q1.
A step-up transformer has 100 turns on its primary coil and 300 turns on its secondary coil. Under what conditions would an input voltage of 240V not produce any output voltage?

Q2. If the magnetic flux passing through a coil changes from .3 webers to .7 webers in .25 secs, What is the EMF induced in a coil of 200 turns?

 

[Hootenanny]

For question two, all you need is Faraday's law.

 

[m2003]

A1. An input voltage of 240V would not produce any output voltage if the transformer is not connected to a power source or if there is a break in the circuit. Additionally, if the transformer is not properly designed or if the primary and secondary coils are not properly aligned, there may not be any output voltage despite an input voltage of 240V.

A2. The formula for calculating EMF (electromotive force) is EMF = -N(dФ/dt), where N is the number of turns in the coil and dФ/dt is the rate of change of magnetic flux. Plugging in the values given in the question, we get EMF = -(200)(0.4/0.25) = -800V. This means that an EMF of 800V would be induced in a coil of 200 turns when the magnetic flux changes from 0.3 webers to 0.7 webers in 0.25 seconds.