Electric & Magnetic Fields Practice Questions Right Hand Grip Rule for Electromagnetism

Lenz’s law of electromagnetic induction is another topic that often seems counterintuitive, because it requiresunderstanding how magnetism and electric fields interact in various situations. Lenz’s law states that the directionof the current induced in a closed conducting loop by a changing magnetic field (Faraday’s Law) is such that thesecondary magnetic field created by the induced current opposes the initial change in the magnetic field that producedit. To apply the right hand rule to cross products, align your fingers and thumb at right angles.

The north end of the solenoid repels the north end of this bar magnet. In the diagram above, the thumb aligns with the z axis, the index finger aligns with the x axis and the middle finger aligns with the y axis. The current in a long, straight vertical wire is in the direction XY, as shown in the diagram.

Right Hand Rule for a Cross Product

The first method I dislike because it creates confusion with the ‘proper’ right hand grip rule which tells us the direction of the magnetic field lines around a long straight conductor and which I’ve written about before . The right-hand right hand grip rule rule dates back to the 19th century when it was implemented as a way for identifying the positive direction of coordinate axes in three dimensions. William Rowan Hamilton, recognized for his development of quaternions, a mathematical system for representing three-dimensional rotations, is often attributed with the introduction of this convention. Following a substantial debate,2 the mainstream shifted from Hamilton’s quaternionic system to Gibbs’ three-vectors system. This transition led to the prevalent adoption of the right-hand rule in the contemporary contexts.

The solenoid will behave exactly like a bar magnet with a clearly defined north and south pole. In vector calculus, it is necessary to relate a normal vector of a surface to the boundary curve of the surface. Since the field lines are heading into this end of the solenoid, we can conclude that the right hand side of this solenoid is, in fact, a south-seeking pole.

The FBI rule is easily remembered by US citizens because of the commonly known abbreviation for the Federal Bureau of Investigation. A different form of the right-hand rule is used in situations where a vector must be assigned to the rotation of a body, a magnetic field or a fluid. Alternatively, when a rotation is specified by a vector, and it is necessary to understand the way in which the rotation occurs, the right-hand rule is applicable. The region inside the solenoid has a very strong and nearly uniform magnetic field. By ‘uniform’ we mean that the field lines are nearly straight and equally spaced meaning that the magnetic field has the same strength at any point. The region outside the solenoid has a magnetic field which gradually weakens as you move away from the solenoid (indicated by the increased spacing between the field lines); its shape is also nearly identical to the ‘butterfly field’ of a bar magnet as mentioned above.

1. Using your right hand, it is possible to predict the direction the current is flowing.
2. By ‘uniform’ we mean that the field lines are nearly straight and equally spaced meaning that the magnetic field has the same strength at any point.
3. One form of the right-hand rule is used in situations in which an ordered operation must be performed on two vectors a and b that has a result which is a vector c perpendicular to both a and b.
4. If the magnetic field is increasing, then the direction of the induced magnetic field vector will bein the opposite direction.
5. We can usethe second right hand rule, sometimes called the right hand grip rule, to determine the direction of the magneticfield created by a current.
6. Luckily, there’s a right hand ruleapplication for torque as well.

Motion, Forces & Energy

To apply the right hand grip rule,align your thumb with the direction of the conventional current (positive to negative) and your fingers will indicate thedirection of the magnetic lines of flux. In the first wire, the flow of positive charges up the pageindicates that negative charges are flowing down the page. Using the right hand rule tells us that the magneticforce will point in the right direction. In the second wire, the negative charges are flowing up the page, whichmeans the positive charges are flowing down the page. As a result, the right hand rule indicates that the magneticforce is pointing in the left direction.

You can do this in reverse by starting your thumb in the direction of the vector and see how your fingers curl to see the direction of rotation. If you point your thumb in the direction of current in a wire, the magnetic field that comes up around it is in the direction of your curling fingers. The right-hand rules assume conventional current, that is… current flows from positive to negative.

Curve orientation and normal vectors

When the magnetic flux through a closed loop conductor changes, it induces a current within the loop. The inducedcurrent creates a secondary magnetic field that opposes the original change in flux that initiated the induced current.The strength of the magnetic field passing through a wire coil determines the magnetic flux. Magnetic flux depends onthe strength of the field, the area of the coil, and the relative orientation between the field and the coil, as shownin the following equation.

1. So we use the convention of the right hand to predict the direction of the fields relative to each other.
2. Since the field lines are heading into this end of the solenoid, we can conclude that the right hand side of this solenoid is, in fact, a south-seeking pole.
3. There is another rule called the right-hand grip rule (or corkscrew rule) that is used for magnetic fields and things that rotate.
4. In ancient times, lodestones were so rare and precious that they were worth more than their weight in gold.
5. Following a substantial debate,2 the mainstream shifted from Hamilton’s quaternionic system to Gibbs’ three-vectors system.

As the current flows upward, the magnetic field will wrap around. All of these rules, in the end, come from the right hand cross product rule anyways. There are lots of things you can do with your right hand, though, so I wouldn’t be surprised if one of them gave you the right direction. For left-handed coordinates, the above description of the axes is the same, except using the left hand; and the ¼ turn is clockwise. In certain situations, it may be useful to use the opposite convention, where one of the vectors is reversed and so creates a left-handed triad instead of a right-handed triad. It helps you remember direction when vectors get cross multiplied.

Magnetic Effect of a Current (Cambridge (CIE) IGCSE Physics)

This is a consequence of Maxwell’s second equation of Electromagnetism (one of a system of four equations developed by James Clark Maxwell in 1873 that summarise our current understanding of electromagnetism). Over many centuries, by patient trial-and-error, humans learned how to magnetise a piece of iron to make a permanent magnet. Yes, the Lorentz force law holds, so whatever rule you’re doing with your right hand must be wrong. One of the best ways to help students become confident using the right hand rule, is to perform a visual demonstration that helps them recognize and correct their misconceptions about orthogonal relationships and coordinate systems. IBO was not involved in the production of, and does not endorse, the resources created by Save My Exams. The typical methods used to identify the N and S poles are shown below.

Thirdly, establish the direction of the field lines using the standard right hand grip rule (3). Unlike most mathematical concepts, the meaning of a right-handed coordinate system cannot be expressed in terms of any mathematical axioms. Rather, the definition depends on chiral phenomena in the physical world, for example the culturally transmitted meaning of right and left hands, a majority human population with dominant right hand, or certain phenomena involving the weak force.