MHT-CET : Physics Entrance Exam

### MHT - CET : Physics - Magnetic Effect of Electric Current Know More

• Galvanometers are instruments used for detecting or measuring current.
• Moving coil galvanometer and moving magnet type galvanometer are two types of galvanometers.
• Moving coil galvanometer is further classified into the D'Arsonval or suspended coil type and the pivoted type.
• Tangent galvanometer is a type of a moving magnet galvanometer.
• The suspended coil type is more accurate and sensitive while the pivoted type is sturdy, compact and portable.
• A galvanometer is converted into an ammeter by connecting a low resistance in parallel with the galvanometer coil.
• A galvanometer is connected into a voltmeter by connecting a high resistance in series with the galvanometer coil.
• When resistors are connected in series, their effective value increases.
• When resistors are connected in parallel, their effective value decreases.
• For a tangent galvanometer, readings are taken between 30° and 60°.
• Accuracy of a tangent galvanometer is maximum for q = 45°.
• Biot Savat's law states that when a current i flows through a small length dl of a conductor, magnetic induction B at a point at a distance r from the element is
 B = m0 ´ Idl sinq 4p r2

• Where
q = angle between current element and position vector of the point.
In vector form:
 = m0I ´ 4p r3
•
•
• The magnetic induction at the centre of a coil of radius r and n turns and carrying current I is
 B = m0 . nI 2 r
• Torque acting on a coil carrying current I when placed in a field of induction B
is
t = nI AB sin q
Where
n = number of turns
A = area of cross section of coil.
•
• Force acting on a charge q moving with a velocity n when placed in a magnetic field of induction B is
F =
q vB sin q
In vector form:
Where
q is the angle between  and  .
• Force acting on a charge of moving with a velocity v when placed in an electric field E is
F =
qE
In vector form:

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