# 7 - Moving charge magnetism and force in magnetic field Questions Answers

CALCULATE THE MAGNETIC FIELD AT THE CENTRE OF SQUARE WIRE OF SIDE (2)^{1/2}cm AND CARRYING A CURRENT OF 10A.?

**Asked By: GAUTAM SAGAR**

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**Joshi sir comment**

method given by BONEY is correct but formula is not correct

it should be **B = 4×{ (μ _{0}I) / 4πR } × [sinθ_{1}+ Sinθ_{2}]**

two short magnets of equal dipole momet M are fastened perpedicularat their centre.the magnitude of magnetic feild at adistance d from the centre on the bisector of right angles is?

**Asked By: AKANKSHA**

**Solved By: SARIKA**

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**Joshi sir comment**

the resultant dipole moment is √2M thus the resultant magnetic field is μ2√2M/4πd^{3} (ans)

this answer is given by sarika and is correct answer

velocity of e^{-} in hydrogen atom is 2X10^{6} m/s . the radius of orbit is 5X10^{-11} m . the mag induction at centre of orbit in T will be??

**Asked By: SARIKA**1 Month ago

**Asked By: SARIKA SHARMA**

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**Joshi sir comment**

B = μ_{0}/2 * i/r

and i = e/T

and T = 2πr/v

solve

potential diff b/w dees of cyclotron is V , if charge q comes out of it after completing n revolution then gain in KE of charge is 2nqV HOW?

**Asked By: SARIKA**1 Month ago

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**Asked By: SARIKA SHARMA**

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**Joshi sir comment**

when charge will move from first dee to second dee it will gain qV and on returning to first dee it will gain qV again so in one revolution it will gain 2qV so in n revolutions it will gain 2qVn

velocity of e^{-} in hydrogen atom is 2X10^{6} m/s . the radius of orbit is 5X10^{-11} m . the mag induction at centre of orbit in T will be??

**Asked By: SARIKA**

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**Joshi sir comment**

B = μ_{0}/2 * i/r

i = e/T

and T = 2πr/v

now solve

A CHARGED PARTICLE IS PROJECTED PARALLEL TO A UNIFORM FIELD . THE PATH OF D PARTICLE WILL BE

1) PARABOLIC

2) ELLIPTICAL

3) CIRCULAR

4) LINEAR

**Asked By: SARIKA SHARMA**

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**Joshi sir comment**

linear and accelerated.

Q 1-when current passes through a solenoid .then what happens to the length of solenoid?

Q2-a current carrying wire carrying current i normally into the paper at the centreof current carring circular ring.the magnetic force acting on the circular ring is ?

Q3- To increase the current through the solenoid from 1A TO 2A ,30J work is done by thr battery.work done by the same battery in increasing the current from 3A TO 4A IS?

Q4- When a closed looop is held stationary in magnetic field b/w north & south pole of 2 permanent magnets of different dipole moments , then current will be induced in the loop or not?

**Asked By: TANVI GROVER**

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**Joshi sir comment**

**1. the length will decrease as the current in the two consecutive turns of the solenoid are in same direction. which will create an atrraction.**

**2. since B produced by the wire is parllel to the direction of dl so net force will be 0**

**3.dw = Lidi first take limit 1 to2 and w=30 to find the L (INTEGERATE)**

** After than again use the above formula taking limit 3 to 4 .put L here ,L= 20**

** the answer is 70J.**

**4. I think no emf will be induced as the flux is not changing.**

**These answers by NIKHIL VARSHNEY are correct **