Question

A crowbar is of length 3 m. Where should the ful-
crum be placed along the length of the crowbar so
that a boulder of 9 kgwt be lifted with it by applying
an effort of 10 N? (g = 10 m s-2)
​

Answer 1

Answer:

A current element is a conductor carrying current.It is the product of current,I and length of very small segment of current carrying wire ,dL.

Let us consider a small element AB of length dl of the conductor RS carrying a current I.

Let r be the position vector of the point P from the current element I dL.and θ be the angle dl and r.

According to Biot-Savarts law,the magnetic field induction dB or magnetic flux density at a point P due to current element depends upon the following factors.

(i) dBI

(ii) dBdl

(iii) dBsinθ

(iv) dB1/r^2

Combining these factors,we get

dBIdLsinθ/r^2

or dB=K Idl sinθ/r^2

where K is a constant of perportionality.

In S.I units, K=μ0/4

thus , dB=μ0/4 I dl sinθ/r^2

where μ0 is absolute premeability of free space and

μ0=4*10^-7 Wb A^-1m^-1

= 4*10^-7*TA^-1m [ 1T=1 Wb m^-2]

In C.G.S units,K=1 (In free space)

Thus dB=Idl sinθ/r^2

In vector form,

dB=μ0/4 I(dl*r)/r^3

magnetic field induction at point P due to current through entire wire is

B=∫μ0/4Idl*r/r^3

Or B=∫μ0/4 Idl sin θ/r^2

Answer 2

Answer:

thanks for free points