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प्रश्न
State the principle of a step-up transformer. Explain, with the help of a labeled diagram, its working ?
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उत्तर
Transformer:
Principle: It is a device which converts high voltage AC into low voltage AC and vice-versa. It is based upon the principle of mutual induction. When alternating current is passed through a coil, an induced emf is set up in the neighbouring coil.
Working: When an alternating current is passed through the primary, the magnetic flux through the iron core changes, which does two things. It produces emf in the primary and an induced emf is also set up in the secondary. If we assume that the resistance of primary is negligible, then the back emf will be equal to the voltage applied to the primary.
`therefore V_1 = -N_1 (dphi)/(dt)`
and`,V_2 = -N_2 (dphi)/dt`
Where, N1 and N2 are number of turns in the primary and the secondary respectively and V1 and V2 are their voltages respectively
In a step-up transformer: N2 > N1, therefore, V2 > V1
संबंधित प्रश्न
Write the function of a transformer.
How much current is drawn by the primary of a transformer connected to 220 V supply when it delivers power to a 110 V − 550 W refrigerator?
What type of current is transmitted from the power station?
The teachers of Geeta’s school took the students on a study trip to a power generating station, located nearly 200 km away from the city. The teacher explained that electrical energy is transmitted over such a long distance to their city, in the form of alternating current (ac) raised to a high voltage. At the receiving end in the city, the voltage is reduced to operate the devices. As a result, the power loss is reduced. Geeta listened to the teacher and asked questions about how the ac is converted to a higher or lower voltage.
1) Name the device used to change the alternating voltage to a higher or lower value. State one cause for power dissipation in this device.
2) Explain with an example, how power loss is reduced if the energy is transmitted over long distances as an alternating current rather than a direct current.
3) Write two values each shown by the teachers and Geeta.
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A step-up transformer converts a low voltage into high voltage. Does it not violate the principle of conservation of energy? Explain.
Mention the various energy losses in a transformer.
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An iron rod is placed parallel to magnetic field of intensity 2000 Am-1. The magnetic flux through the rod is 6 × 10−4 Wb and its cross-sectional area is 3 cm2. The magnetic permeability of the rod in Wb A-1m-1 is ______.
A step down transformer connected to an AC mains supply of 220 V is made to operate at 11 V, 44 W lamp. Ignoring power losses in the transformer, what is the current in the primary circuit?
