NEET Class neet Answered

Force on a current carrying conductor in a magnetic field is given I(LxB). As the cross product is between B and L so to find direction of force we should use effective length(L) and B in right hand thumb rule then why we use direction of current and B in right hand thumb rule?

Asked by rohitraman1115 | 12 Mar, 2021, 03:04: AM

Expert Answer

Fleming's left hand rule is applied when we get mechanical force on a conductor when electrical current is passing through conductor

due to interaction of electric current with magnetic field .

By applying this rule, we get the direction of motion of conductor by knowing the direction of current and direction of magnetic field.

According to this rule, stretch the thumb, forefinger and middle finger of your left hand such that they are mutually perpendicular
If the first finger points in the direction of magnetic field and the second finger in the direction of current, then the thumb will point

in the direction of motion or the force acting on the conductor.

Fleming's Right hand rule is applied when we get induced current using movement of conductor in magnetic field

This rule states that if we stretch the thumb, forefinger and middle finger of right hand so that they are perpendicular to each other
such that If the forefinger indicates the direction of the magnetic field and the thumb shows the direction of motion of conductor,

then the middle finger will show the direction of induced current.

Why we need right hand thumb rule? Answer to this question is when consuctor is moved in magnetic field, we get induced current.

Where as to get mechanical force we use current from electrical power supply or from EMF of battery.

In any device, applied current and induced current are opposite in direction . Hence for applied current we use left-hand rule and

for induced current we use right hand rule.

Answered by Thiyagarajan K | 12 Mar, 2021, 03:50: PM