Tue July 17, 2012 By:

1. what will happen if compass needle in oersted experiment is kept perpendicularly to current carrying conductor, whether the needle deflects or not give the reason? 2. Is there no magnetic field in the blank spaces in magnetic field line? 3.why do the armature coil in electric motor is taken in rectangular shape not in other shape? 4.what is the difference between Alternating Current and Direct Current and also what is the need to change the D.C. and A.C. in our home appliances? 5.why the voltmeter connected parallel in the circuit and ammeter in series in the circuit?

Expert Reply
Tue July 17, 2012
1. The magnetic field lines are perpendicular to the direction of current in  a consuctor. So the needel will be in allignment, it wont deflect.
2. Ther is no such thing as blank spaces in magnetic field lines. There are always field every where. It is a continuous function. Not discreet.
3. It can be taken in any shape. It is just rectangular is most easy to get in a tight coil. However coil do exist in other shapes also like circular etc. depending on usage.
4. In AC current the potential difference varies sinosoudly with the time. and in DC it is constant. Some of our home appliance works on DC some of them work on AC so thats why we need to change.
5. Voltmeter has very large resistance and is used to measure the potentil difference accross a system and is thus connected in parallel where as ammeter has negligiable resistance and is used to measure current in  a circuit and this connected in series.
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