Bissoy.com
Doctors Medicines MCQs Q&A

A circular loop placed in a plane perpendicular to the plane of paper carries a current when the key is ON. The current as seen from points A and B (in the plane of paper and on the axis of the coil) is anti-clockwise and clockwise respectively. The magnetic field lines point from B to A. The N-pole of the resultant magnet is on the face close to

A circular loop placed in a plane perpendicular to the plane of paper carries a current when the key is ON. The current as seen from points A and B (in the plane of paper and on the axis of the coil) is anti-clockwise and clockwise respectively. The magnetic field lines point from B to A. The N-pole of the resultant magnet is on the face close to Correct Answer A

CONCEPT:

  • Current Loop As a Magnetic Dipole: A current-carrying circular coil behaves like a bar magnet whose magnetic moment is

M = NIA

Where N = number of turns in the coil, I = Current through the coil and A = Area of the coil

  • The right-hand thumb rule of circular currents: According to this rule if the direction of current in the circular conducting coil is in the direction of folding fingers of the right hand, then the direction of the magnetic field will be in the direction of the stretched thumb.

[ alt="F1 P.Y Madhu 13.05.20 D6" src="//storage.googleapis.com/tb-img/production/20/05/F1_P.Y_Madhu_13.05.20_D6.png" style="width: 270px; height: 137px;">

EXPLANATION:

  • The magnetic field lines point from B to A this implies that magnetic field lines enter from B and emerge out from A and we know from the case of a bar magnet that the internal direction of magnetic field is from south to north pole.

[ alt="Magnetism ALP Rishi 12Q Part 1 Hindi - Final images Q3a" src="//storage.googleapis.com/tb-img/production/18/11/Magnetism%20ALP_Rishi_12Q_Part_1_Hindi%20-%20Final_images_Q3a.PNG" style="width: 208px; height: 107px;">

  • If the direction of current in the circular current loop is in an anticlockwise direction, then the top face of the coil will behave as North pole and opposite face behaves as the south pole.

[ alt="F1 P.Y Madhu 13.05.20 D7" src="//storage.googleapis.com/tb-img/production/20/05/F1_P.Y_Madhu_13.05.20_D7.png" style="width: 172px; height: 207px;">

  • Thus, face close to A is the north pole, and close to B is the south pole.

The trick to remember:

If looking into a loop direction of current is

Anticlockwise – Face acts as NORTH POLE

clockwise – Face acts as SOUTH POLE

Related Questions

A current carrying coil having magnetic moment M is placed in a magnetic field B. Initially the magnetic field is perpendicular to the plane of the coil and then coil turned about an axis such that the angle between the magnetic field and the plane of the coil become zero. Then choose the correct statement.
Consider the following statement: a) Magnetic field lines are always form closed curve. b) Magnetic field lines start from north pole outside the magnet c) Magnetic field lines start from south pole outside the magnet Which of the following is a property of magnetic field lines?
A circular current carrying loop is placed in a uniform magnetic field of magnitude B. The angle between the plane perpendicular to the coil and the magnetic field is θ. The current in the loop is I. Then the torque on the circular loop will be-
A circular current carrying loop is placed in a uniform magnetic field B which is perpendicular to the plane of the circular loop. Find the force on the circular loop of radius R and the current in the loop is I.
A rectangular current carrying loop is placed in a uniform magnetic field of magnitude B. The angle between the plane perpendicular to the coil and the magnetic field is θ. The current in the loop is I. Then the torque on the rectangular loop will be-
A circular coil is suspended in a uniform magnetic field of induction 7 × 10¯⁵ T whose radius is 16 cm and it has 80 turns that carries 6 A current. Calculate the torque acting on the circular coil when the plane of the coil is 45° normal with the magnetic field.
How far is point 'R' from Point 'T'? Statement (I): Point 'R' is 5 metres to the north of point 'M'. Point 'U' is 4 metres to the east of point 'R'. Point 'T' is to the west of point 'R' such that points 'U' 'R' and 'T' form a straight line of  metres. Statement (II): Point 'Z' is metres to the south of point 'T'. Point 'U' is  metres to the east of point 'T'. Point 'M' is  metres to the east of point 'Z'. Point 'R' is  metres to the north of point 'M'. Point 'R' lies on the line formed by joining points 'T' and 'U'.
In the following question, sentences of a paragraph have been jumbled and labelled as A, B, C and D. You are required to rearrange the jumbled sentences of the paragraph and mark your response accordingly by selecting the correct option. A: The magnetic field disappears when the current is turned off. B: A current through the wire creates a magnetic field which is concentrated in the hole, denoting the center of the coil. C: An electromagnet is a type of magnet in which the magnetic field is produced by an electric current.  D: Electromagnets usually consist of wire wound into a coil. 
Consider a conducting loop of radius a and total loop resistance R placed in a region with a magnetic field B thereby enclosing a flux $${\phi _0}$$ . The loop is connected to an electronic circuit as shown, the capacitor being initially uncharged.
Electromagnetic Theory mcq question image
If the loop is pulled out of the region of the magnetic field at a constant speed u, the final output voltage Vout is independent of
Two circular dials of exactly the same size are mounted on a wall side by side in such a way that their perimeters touch at one point. Dial 1, which is on the left , spins clockwise around its center , and dial 2 , which is on the right spins counter clockwise around its center . (Assume that there is no friction at the point of contact between the dials.) Each dial is marked on its perimeter at three points that are at equale distances around the points arked ondial 1 are N, O, and P and the points marked on dial 2 are X, Y, and Z. If points O and Z are just meeting at the point of contact between the dials , and if dial 1 spins at the same speed as dial 2, what is the smallest number of revolutions of each dial that will bring O and Z together again?