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12th Grade > Physics

MAGNETIC EFFECTS OF CURRENT MCQs

Magnetic Effects Of Electric Current, Magnetic Effects Of Current(10th And 12th Grade)

Total Questions : 54 | Page 1 of 6 pages
Question 1. Two infinite length wires carries currents 8A and 6A respectively and placed along X and Y-axis. Magnetic field at a point P(0,0,d)m will be
  1.    7μ0πd
  2.    10μ0πd
  3.    14μ0πd
  4.    5μ0πd
 Discuss Question
Answer: Option D. -> 5μ0πd
:
D
Magnetic field due to P due to wire 1, B1=μ04π.2(8)d
Two Infinite Length Wires Carries Currents 8A And 6A Respect...
and due to wire 2, B2=μ04π.2(6)d
Bnet=B21+B22
=(μ04π.16d)2+(μ04π.12d)2
=μ04π×2d×10=5μ0πd
Question 2. An infinitely long straight conductor is bent into the shape as shown in the figure. It carries a current of i ampere and the radius of the circular loop is r metre. Then the magnetic induction at its centre will be
An Infinitely Long Straight Conductor Is Bent Into The Shape...
  1.    μ04π2ir(π+1)
  2.    μ04π.2ir(π−1)
  3.    Zero
  4.    Infinite
 Discuss Question
Answer: Option B. -> μ04π.2ir(π−1)
:
B
The given shape is equivalent to the following diagram
The field at o due to straight part of conductor is B1=μ04π.2ir.
An Infinitely Long Straight Conductor Is Bent Into The Shape...
The field at o due to circular coil isB2=μ04π.2πir. Both fields will act in the opposite direction, hence the total field at O.
i.e. B=B2B1=(μ04π)×(π1)2ir=μ04π.2ir(π1)
Question 3. A laboratory has very strong magnetic field upwards, i.e. towards the ceiling. An electron gun is fired towards a wall. The electron will:
A Laboratory Has Very Strong Magnetic Field Upwards, I.e. To...
  1.    Hit the other wall along the same line.
  2.    Hit the ceiling.
  3.    Hit the ground.
  4.    Hit the wall on the left side of the shooter.
 Discuss Question
Answer: Option D. -> Hit the wall on the left side of the shooter.
:
D
The answer can be found out using Fleming's left-hand rule:
According to the order:Thumb - Force, Forefinger is Magnetic Field, Middle finger- Current. The direction of current is always opposite to the direction of flow of electrons.
The electrons will move towards the wall which is on the left side of the shooter.
A Laboratory Has Very Strong Magnetic Field Upwards, I.e. To...
Question 4. Through two parallel wires x and y, currents of 10A and 2A, respectively are passed in opposite directions. X is infinitely long and y has a length of 2m. The distance between them is 10cm. The magnetic force on y is
 
  1.    4×10−5N
  2.    4×10−6N
  3.    8×10−5N
  4.    8×10−6N
 Discuss Question
Answer: Option C. -> 8×10−5N
:
C
F=μ0i,i2l2πr=2×107×10×2×210×102F=8×105N
Question 5. A long vertical wire carrying a current of 1A in the upward direction is placed in a region where a horizontal magnetic field of 2.0×104T exists from south to north. Find the point where the resultant magnetic field is zero.
  1.    1.0mm, to the west of the wire
  2.    1.0 mm, to the East of the wire
  3.    2.0 mmm to the North of the wire
  4.    2.0 mm, to the South of the wire
 Discuss Question
Answer: Option A. -> 1.0mm, to the west of the wire
:
A
B=BHμ0i2πr=BH2×107×1r=2.0×104
r=103mwest of the wire
= 1.0 mm west of the wire
A Long Vertical Wire Carrying A Current Of 1A In The Upward ...
Question 6. In the figure, AB is a long straight wire carrying a current of 20A and CDFG is a rectangular loop of size 20 cm x 9cm carrying a current of 10A. The edge CG is parallel to AB, at a distance of 1cm from it. The force exerted on the loop by the magnetic field of the wire is
In The Figure, AB Is A Long Straight Wire Carrying A Current...
  1.    3.6×10−4N attraction
  2.    3.6×10−4N epulsion
  3.    7.2×10−4N attraction
  4.    7.2×10−4N repulsion
 Discuss Question
Answer: Option C. -> 7.2×10−4N attraction
:
C
F=μ0i1i2l2π[1r11r2]=2×107×20×10×0.2[1102110×102]=8×106×[910]×102=7.2×104N
Question 7. A coil having N turns is wound tightly in the form of a spiral with inner and outer radii a and b respectively. When a current I passes through the coil, the magnetic field at the centre is
  1.    μ0NIb
  2.    2μ0NIa
  3.    μ0NI2(b−a)lnba
  4.    μ0IN2(b−a)lnba
 Discuss Question
Answer: Option C. -> μ0NI2(b−a)lnba
:
C
Number of turns per unit width =Nba
Consider an elemental ring of radius x and with thickness dx Number of turns in the ring =dN=Ndxba
Magnetic field at the center due to the ring element
dB=μ0(dN)i2x=μ0i2.Ndx(ba).1x
Field at the centre
=dB=μ0NI2(ba)badxx
=μ0Ni2(ba)lnba.
A Coil Having N Turns Is Wound Tightly In The Form Of A Spir...
Question 8. If a copper rod carries a direct current, the magnetic field associated with the current will be
  1.    Only inside the rod
  2.    Only outside the rod
  3.    Both inside and outside the rod
  4.    Neither inside nor outside the rod
 Discuss Question
Answer: Option C. -> Both inside and outside the rod
:
C
Magnetic field lies inside as well as outside the solid current carrying conductor.
Question 9. A magnetic field can be produced by       
  1.    A moving charge 
  2.    A changing electric field
  3.    None of these  
  4.    Both moving charge & changing electric field 
 Discuss Question
Answer: Option D. -> Both moving charge & changing electric field 
:
D
A moving charge and changing electric field both produces magnetic field.
Question 10. In the figure given below, a coil is placed between two permanent magnets and it is rotated with the help of an axle on which two rings R1 and R2 are internally attached. B1 and B2 represent metallic brushes. G represents galvanometer.
In The Figure Given Below, A Coil Is Placed Between Two Perm...
As the coil starts to rotate, the current flows through ABCD as shown. The coil is rotating in:
  1.    Clockwise direction
  2.    Anti-clockwise direction
  3.    Either Clockwise or anti-clockwise
  4.    Can't be said
 Discuss Question
Answer: Option A. -> Clockwise direction
:
A
Using Fleming's right-hand rule, point your index finger of your right hand towards the direction of the magnetic field i.e. from north to south. Middle finger towards the direction of the current. You can now see that the thumb points upwards which tell that the coil rotates in a clockwise direction.

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