Magnetic Effect of a Current Cambridge CIE IGCSE Physics Revision Notes 2021

In this model, your fingers point in the direction of the magnetic field, your thumb points in the direction of theconventional current running through the wire, and your palm indicates the direction that the wire is being pushed (force). In fact – if you trace the magnetic field with a compass, you can see that it matches the behavior a bar magnet perfectly.Using a third right-hand rule, we can we predict which side of the coil is north.Let your curling fingers be the direction the current is flowing. To understand how Lenz’s Law will affect this system, we need to first determine whether the initial magnetic field isincreasing or decreasing in strength. As the magnetic north pole gets closer to the loop, it causes the existing magneticfield to increase. Since the magnetic field is increasing, the induced current and resulting induced magnetic field willoppose the original magnetic field by reducing it.

Right Hand Rule for Magnetism

If the velocity of the charged particle is parallel to the magnetic field (or antiparallel), then there is no force because sin(θ) equals zero.When this occurs, the charged particle can maintain its straight line motion, even in the presence of a strong magnetic field. 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. The right-hand rule imposes the following procedure for choosing one of the two directions. There is another rule called the right-hand grip rule (or corkscrew rule) that is used for magnetic fields and things that rotate. If you have two vectors that you want to cross multiply, you can figure out the direction of the vector that comes out by pointing your thumb in the direction of the first vector and your pointer in the direction of the second vector. Your middle finger will point the direction of the cross product.

Applications of the magnetic effect of a current

Although these currents are moving in opposite directions, a singlemagnetic force is observed acting on the wire. Therefore, the force occurs in the same direction whether weconsider the flow of positive or negative charge carriers in the above image. To apply the right hand rule to Lenz’s Law, first determine whether the magnetic field through the loop is increasing ordecreasing. Recall that magnets produce magnetic field lines that move out from the magnetic north pole and in toward themagnetic south pole. If the magnetic field is increasing, then the direction of the induced magnetic field vector will bein the opposite direction. If the magnetic field in the loop is decreasing, then the induced magnetic field vector willoccur in the same direction to replace the original field’s decrease.

So we use the convention of the right hand to predict the direction of the fields relative to each other. If we consider current flow as the movement of positive charge carriers (conventional current) in the aboveimage, we notice that the conventional current is moving up the page. Since a conventional current is composedof positive charges, then the same current-carrying wire can also be described as having a current with negativecharge carriers moving down the page.

Effects of Forces

For the flow of currents, which are the imagined flow of positive charge, it is appropriate to use your right hand. But when it comes to negative currents, such as electrons, it is appropriate to use your left hand, which generates the opposite result that a positive charge would experience. If one wishes to demonstrate the Lorentz force on a CRT, it helps to know to emphasize “use the left-hand rule for negative charges.”

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. It helps you remember direction when vectors get cross multiplied.
2. 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.
3. Thirdly, establish the direction of the field lines using the standard right hand grip rule (3).
4. 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).
5. To apply the right hand rule to cross products, align your fingers and thumb at right angles.
6. 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.

Teaching electricity and magnetism is complicated by the challenge that the magnetic forces are perpendicular to the motion of the particles and currents. This requires a three-dimensional perspective which can introduce a variable of a “wrong” direction. To prevent errors, let us be “right” and use the right-hand rule.Some would claim that there is only one right-hand rule, but I have found the convention of three separate rules for the most common situations to be very convenient. These are for (1) long, straight wires, (2) free moving charges in magnetic fields, and (3) the solenoid rule – which are loops of current. We use rules to help us solve problems, laws would be the underlying cause as to why the rules work.Electricity and Magnetism are connected phenomena, but at right angles to each other.

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This means that the primary and secondary magnetic fields will occur inopposite directions. When the existing magnetic field is decreasing, the induced current and resulting induced magneticfield will oppose the original, decreasing magnetic field by reinforcing it. Thus, the induced magnetic field will have thesame direction as the original magnetic field.

For example, some high schools use the “left-hand” rules because it deals with ELECTRON FLOW, that is… current flow from negative to positive (the direction that electrons flow from a battery for example). I always thought the same could be applied to the opposite scenario. The right hand grip rule (also known as right hand screw rule) tells you the direction of a magnetic field due to a current. If you point your thumb in the direction of the current, your fingers will curl in the direction of the magnetic field.

1. 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 .
2. While a magnetic field can be induced by a current, a current can also be induced by a magnetic field.
3. A current-carrying coil will create a magnetic field as shown below.
4. To understand how Lenz’s Law will affect this system, we need to first determine whether the initial magnetic field isincreasing or decreasing in strength.
5. 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.
6. In the second wire, the negative charges are flowing up the page, whichmeans the positive charges are flowing down the page.
7. Teaching electricity and magnetism is complicated by the challenge that the magnetic forces are perpendicular to the motion of the particles and currents.

Next, align your thumb in the direction of theinduced magnetic field and curl your fingers. Since electric current is made of moving charges we can also push it around with magnets. This will highlight that the current, field, and force are all three at right angles.Using your right hand, the current flows from positive to negative – thumb. The magnetic field – pointer finger – is directed from North to South (that usually means from red to blue). The force on the current is perpendicular to both of these right hand grip rule and is predicted by your middle fingerThis 2nd rule is usually called the Lorentz Force named after H.