# Electronics and Communication Engineering - Electronic Devices and Circuits - Discussion

Discussion Forum : Electronic Devices and Circuits - Section 8 (Q.No. 1)

1.

**Assertion (A):** Hall effect is used to find the type of semiconductor.

**Reason (R):** When a specimen of semiconductor carrying current I lies in a magnetic field the force on electrons and holes is in opposite directions.

Discussion:

1 comments Page 1 of 1.
Joshnavi said:
4 years ago

When a current. Carrying semiconductor is placed in a magnetic field charge inside the semiconductor experience a force which is perpendicular to both magnetic field and current.

Here,

Lorenz force( f) = q *( v * B) ----> (1)

In a semiconductor electric field is also present due to electrons so electric force.

F(e)= q E ----> (2)

Solving ...

V*B = E ----> (3)

Since E= v/t

V*B=v/t ----> (4)

Since, J = q * n * v

V = J/q*n .. Substitute in eq 4.

VB = (J/qnt)

Since, J = current (i)/ Area of semiconductor(A)

A= thickness of semiconductor * width of the semiconductor

A= w * t

J = I / w t

So;

( I * B )/(w q n) = V. Hall voltage

Hall coefficient R=(1/ qn )

R = v * w / (B * I )

R is inversely proportional to I and B.

For n-type semiconductor, electrons accommodate at bottom of a semiconductor due to opposite force.

For p-type semiconductor, electrons accommodate at top of the semiconductor.

Here,

Lorenz force( f) = q *( v * B) ----> (1)

In a semiconductor electric field is also present due to electrons so electric force.

F(e)= q E ----> (2)

Solving ...

V*B = E ----> (3)

Since E= v/t

V*B=v/t ----> (4)

Since, J = q * n * v

V = J/q*n .. Substitute in eq 4.

VB = (J/qnt)

Since, J = current (i)/ Area of semiconductor(A)

A= thickness of semiconductor * width of the semiconductor

A= w * t

J = I / w t

So;

( I * B )/(w q n) = V. Hall voltage

Hall coefficient R=(1/ qn )

R = v * w / (B * I )

R is inversely proportional to I and B.

For n-type semiconductor, electrons accommodate at bottom of a semiconductor due to opposite force.

For p-type semiconductor, electrons accommodate at top of the semiconductor.

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