There are two conductors X and Y carrying a current I and moving in the same direction. p and q are two electron beams also moving in the same direction. Will there be attraction or repulsion between the 2 conductors and between the two electron beams separately?

The electron beams will attract each other and the conductors repel each other

The electron beams will repel each other and conductors attract each other

The electron beams will attract each other and the conductors also attract each other

The electron beams will attract each other and the conductors repel each other

The electron beams will repel each other and the conductors also repel each other

What is the expression for the force experienced by two parallel current carrying conductors of unequal length?

F= ( frac { mu_o}{4 pi } times frac {I_1 I_2}{r} ) l

F= ( frac { mu_o}{4 pi } times frac {2I_1 I_2}{r} ) l

F= ( frac { mu_o}{4 pi } times frac {I_1 I_2}{r} ) l

F= ( frac { mu_o}{4 pi } times frac { frac {2I_1 I_2}{r}}{l} )

F= ( frac { mu_o}{4 pi } times frac {2I_1 I_2}{4r} ) l

1.	Pick out the expression for force per unit length between two parallel carrying conductors if the current passing through both of them are the same?
A.	( frac { mu_o 2I^2}{4 b} )
B.	( frac { mu_o 2I^3}{4 b} )
C.	( frac { mu_o I^2}{4 b} )
D.	( frac { mu_o 4I^2}{4 b} )
Answer» C. ( frac { mu_o I^2}{4 b} )

2.	There are 2 long parallel conductors AB and CD. AB carries 4A current and CD carries 3A current. The magnetic field at the midpoint of these 2 conductors is B. If 4A current is switched off, then what is the magnetic field at the midpoint now?
A.	( frac {B}{3} )
B.	( frac {2B}{3} )
C.	B
D.	3B
Answer» E.

3.	Two long conductors, separated by a distance r carry current I₁ and I₂ in the same direction. They exert a force F on each other. Now, the current in one them is increased to 3 times and the direction is reversed. The distance is also increased to 5r. What is the new value of the force between them?
A.	( frac {3F}{5} )
B.	( frac {-3F}{5} )
C.	( frac {5F}{3} )
D.	( frac {-5F}{3} )
Answer» C. ( frac {5F}{3} )

4.	When infinitely long parallel wires carry equal currents in the same direction, the magnetic field at the midpoint in between the two wires is zero.
A.	True
B.	False
Answer» B. False

5.	There are two conductors X and Y carrying a current I and moving in the same direction. p and q are two electron beams also moving in the same direction. Will there be attraction or repulsion between the 2 conductors and between the two electron beams separately?
A.	The electron beams will repel each other and conductors attract each other
B.	The electron beams will attract each other and the conductors also attract each other
C.	The electron beams will attract each other and the conductors repel each other
D.	The electron beams will repel each other and the conductors also repel each other
Answer» C. The electron beams will attract each other and the conductors repel each other

6.	Two parallel, long wires carry currents I₁ and I₂ where I₁ > I₂. When the currents are in the same direction, the magnetic field at a point midway between the wires is 50 T. If the direction of I₂ is revered, the field becomes 100 T. What is the value of ( frac {I_1}{I_2} )?
A.	1
B.	2
C.	3
D.	4
Answer» D. 4

7.	What is the expression for the force experienced by two parallel current carrying conductors of unequal length?
A.	F= ( frac { mu_o}{4 pi } times frac {2I_1 I_2}{r} ) l
B.	F= ( frac { mu_o}{4 pi } times frac {I_1 I_2}{r} ) l
C.	F= ( frac { mu_o}{4 pi } times frac { frac {2I_1 I_2}{r}}{l} )
D.	F= ( frac { mu_o}{4 pi } times frac {2I_1 I_2}{4r} ) l
Answer» B. F= ( frac { mu_o}{4 pi } times frac {I_1 I_2}{r} ) l