Thumb Rule And Right Hand Rule
Thumb rule and right hand rule are for conventional current or electron flow ?
In a real experiment for finding true N , S what should I do?
When considering Lorentz force, right hand rule is for negative charges, so electrons. Left hand rule is for conventional current. The field finger points in the direction of the field lines, which is the direction a north pole would move if it were in that position. Remember “thumb rule” instead like a corkscrew or door key. The way you turn the key into the door is the circular locus the magnetic field would take. Since north poles repel each other, the field finger points towards the south pole. Then naturally from dipole law, opposite direction must lead to a north pole.
In a winding, use a right hand grip rule . Conventional current flows in the direction of the fingers, then magnetic field within the winding is in the direction of the thumb.
The rule also works for magnetic field around a current. Thumb in the direction of current, fingers curl in the direction the field goes.
To test whether a pole is north or south, set up the coil and battery and see what happens. Or use the Earth, always remembering that because the North pole of a magnet points roughly geographically north, the Earth’s North Magnetic Pole is, in magnetic terms, a south pole.
Left Or Right Hand Rule
I’m currently looking at the right hand rule for magnetism, and have got myself a bit mixed up. I was originally taught to use the left hand rule, with the acronym FBI: Force for the thumb, B field for the first finger, and current for the middle finger.
Since current flows in the opposite direction to electrons, shouldn’t this work for magnetic forces on moving partciles? Yet all my textbooks use the right hand rule.
A summary of which rule is appropriate for which case would be ideal!
- 1$\begingroup$Your left hand rule works for negatively charged particles. For positively charged particles or conventional current use the right hand rule.$\endgroup$
What Is The Right Hand Rule In Physics
The law of the right hand states that the thumb of the right hand point in the direction of v, the fingers in the direction of B and the force are guided perpendicular to the right hand palm in order to locate the direction of the magnetic force on a positive moving charge.
It works because to calculate the force the magnetic field exerts on a current, we use the same right hand law. And it is often the case that pairs that make the measurable consequence not random exist in these kinds of right/left hand laws.
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Currents Induced By Magnetic Fields
While a magnetic field can be induced by a current, a current can also be induced by a magnetic field. 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. To use the right hand grip rule, point your right thumb in the direction of the current’sflow and curl your fingers. The direction of your fingers will mirror the curled direction of the induced magnetic field.
The right hand grip rule is especially useful for solving problems that consider a current-carrying wire or solenoid.In both situations, the right hand grip rule is applied to two applications of Ampere’s circuital law, which relatesthe integrated magnetic field around a closed loop to the electric current passing through the plane of the closed loop.
Left Hand Rule Or Right Hand Rule: Differences
Unlike the right-hand rule, the left hand rule is always used when the flow of electrodes goes from + to -. In concrete terms, this means that the left hand rule is always used when talking about electric current with negative charge carriers. The right-hand rule thus starts from positively charged particles, so-called cations.
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Right And Left Hand Rules
No fancy movement in this tutorial, but these rules come in very handy when trying to understand some of whats going on in our other tutorials.
Youll find two of the most useful tools for understanding electromagnetism right at the end of your arms.
Right hand rule.
These convenient appendages help us understand the interaction between electricity and magnetism via the Right Hand Rule and the Left Hand Rule.
The Right Hand Rule, illustrated at left, simply shows how a generates a magnetic field. If you point your thumb in the direction of the current, as shown, and let your fingers assume a curved position, the magnetic field circling around those wires flows in the direction in which your four fingers point.
The Left Hand Rule shows what happens when an electrical current enters a magnetic field. You need to contort your hand in an unnatural position for this rule, illustrated below. As you can see, if your index finger points in the direction of a magnetic field, and your middle finger, at a 90 degree angle to your index, points in the direction of the current, then your extended thumb points in the direction of the force exerted upon that particle. This rule is also called Fleming’s Left Hand Rule, after English electronics pioneer , who came up with it.
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\hat y \times \hat x = – \hat z y^×x^=z^
The former leads to a right-handed coordinate system and the latter leads to a left-handed coordinate system represented by right-hand rules and left-hand rules respectively.
Figure: right-handed and left-handed coordinates.
Orientation of a curve: The orientation of a curve is expressed in terms of the normal to the surface bounded by the curve. For a positively oriented curve, the thumb of the right hand represents the normal to the surface when the other four fingers curl along the orientation or the boundary curve. For a negatively oriented curve, the same is represented by the left hand.
Figure: Right-hand grip rule and orientation of a curve .
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Fleming’s Left Hand Rule And Right Hand Rule
When a current-carrying conductor is placed under a magnetic field, a force acts on the conductor. The direction of this force can be identified using Flemings Left Hand Rule. Likewise, if a moving conductor is brought under a magnetic field, electric current will be induced in that conductor. The direction of the induced current can be found using Flemings Right Hand Rule. It is important to note that these rules do not determine the magnitude, instead show only the direction of the three parameters when the direction of the other two parameters is known. Flemings Left-Hand Rule is mainly applicable to electric motors and Flemings Right-Hand Rule is mainly applicable to electric generators.
Direction Associated With An Ordered Pair Of Directions
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 most common example is the vector cross product. The right-hand rule imposes the following procedure for choosing one of the two directions.
- With the thumb, index, and middle fingers at right angles to each other , the middle finger points in the direction of c when the thumb represents a and the index finger represents b.
Other finger assignments are possible. For example, the first finger can represent a, the first vector in the product the second finger, b, the second vector and the thumb, c, the product.
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Right Hand Rule For Torque
Torque problems are often the most challenging topic for first year physics students. Luckily, there’s a right hand ruleapplication for torque as well. To use the right hand rule in torque problems, take your right hand and point it in thedirection of the position vector , then turn your fingers in the direction of the force and your thumb will pointtoward the direction of the torque.
The equation for calculating the magnitude of a torque vector for a torque produced by a given force is:
When the angle between the force vector and the moment arm is a right angle, the sine term becomes 1 and the equationbecomes:
F = force r = distance from center to line of action
Difference Between Flemings Left
Left-Hand Rule | |
It was invented by John Ambrose Fleming |
It was invented by John Ambrose Fleming |
It is used for electric motors |
It is used for electric generators |
The purpose of the rule is to find the direction of motion in an electric motor |
The purpose of the rule is to find the direction of induced current when a conductor moves in a magnetic field. |
The thumb represents the direction of the thrust on the conductor |
The thumb represents the direction of motion of the conductor |
The index finger represents the direction of the Magnetic Field |
The index finger represents the direction of the Magnetic Field |
The middle finger represents the direction of the current |
The middle finger represents the direction of the induced current |
From this, we can observe that the left hand satisfies Motor, and the right hand Generator. The Flemings left-hand rule and Flemings right-hand rule are a pair of visual mnemonics . In practice, these rules are never used except as a convenient trick to determine the direction of the resultant either current or thrust. What gives the magnitude of force along this direction determined by these rules is the Lorentz Force.
Flemings Left-Hand Rule Examples
Q1. Determine the direction of the force acting on the proton, if the proton moves towards the east by entering a uniform magnetic field in the downward direction.
Answer:
Using Flemings left-hand rule, we can determine the direction of force acting on the proton.
Answer:
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What Is The Right
The right-hand rule or three-finger rule is an aid that illustrates vectors within a three-dimensional coordinate system. This help is used in different areas of mathematics and physics:
- In the geometry for orientation of a vector or vector point from the cross product of a coordinate system.
- To determine the direction of the angular momentum in the rotation of bodies.
- In physics in the context of electromagnetism and electrical engineering as the cause-mediation-effect rule . It is also described in this context as a corkscrew rule or right-fist rule.
Right Hand Rule In Physics
The right hand rule is a hand mnemonic used in physics to identify the direction of axes or parameters that point in three dimensions.Invented in the 19th century by British physicist John Ambrose Fleming for applications in electromagnetism, the right hand rule is mostoften used to determine the direction of a third parameter when the other two are known .There are a few variations of the right hand rule, which are explained in this section.
When a conductor, such as a copper wire, moves through a magnetic field , an electric current is induced in the conductor.This phenomenon is known as Faraday’s Law of Induction. If the conductor is moved inside the magnetic field, then there is a relationshipbetween the directions of the conductor’s motion , magnetic field and the induced current. We can use Fleming’s right hand ruleto investigate Faraday’s Law of Induction, which is represented by the equation:
emf = induced emf N = number of turns of coilB = change in the magnetic flux t = change in time
Because the x, y and z axes are perpendicular to one another and form right angles, the right hand rule can be used to visualize theiralignment in three-dimensional space. To use the right hand rule, begin by making an L-shape using your right thumb, pointer and middlefinger. Then, move your middle finger inwards toward your palm, so that it is perpendicular to your pointer finger and thumb. Your handshould look similar to this:
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Positive And Negative Torques
Torques that occur in a counter clockwise direction are positive torques. Alternatively, torques that occur in theclockwise direction are negative torques. So what happens if your hand points in or out of the paper? Torques thatface out from the paper should be analyzed as positive torques, while torques that face inwards should be analyzedas negative torques.
Three Right Hand Rules Of Electromagnetism
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 long, straight wires, free moving charges in magnetic fields, and the solenoid rule which are loops of current. Calling these “rules” is the right name. They are not laws of nature, but conventions of humankind. We use rules to help us solve problems, laws would be the underlying cause as to why the rules work.
Danish Physicist and Chemist Hans Christian Ørsted
Rule #1 Oersted’s Law
Our story begins with Oersted’s Demonstration, which was performed for the first time during a lecture in 1821. What Oersted showed for the first time that when a current carrying wire passes over a compass the needle which is a magnet the needle deflects. When it is underneath the magnet it deflects the other way. The direction that the magnet points is parallel to the magnetic field around the wire. And you can predict that with your right hand!
Rule #2 The Lorentz Force
Now, some people and some books prefer to use the palm to represent the force, that would be current field force .
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Right Hand Rule For A Cross Product
A cross product, or vector product, is created when an ordered operation is performed on two vectors, a and b. Thecross product of vectors a and b, is perpendicular to both a and b and is normal to the plane that contains it. Sincethere are two possible directions for a cross product, the right hand rule should be used to determine the directionof the cross product vector.
For example, the cross product of vectors a and b can be represented using the equation:
To apply the right hand rule to cross products, align your fingers and thumb at right angles. Then, point your indexfinger in the direction of vector a and your middle finger in the direction of vector b. Your right thumb will pointin the direction of the vector product, a x b .
Why Does The Right Hand Rule Work For Determining The Direction Of Magnetic Field Around A Straight Current Carrying Wire
According to right hand rule, If I put my thumb in the direction of the current flow and encircle myt other fingers, the direction of those finger will refer to the direction of the magnetic field. But why does this work?
I mean, why is the magnetic field created in that direcrion?
- 1$\begingroup$This question is not, properly speaking, a duplicate of this other question, but in my answer to this other question I basically derived why the definition of magnetic field $F = q $ and the right-hand-rule definition of $\times$ implies this right-hand-rule for how fields rotate around a moving line of charge, from the observation that like-moving lines of charge attract while opposite-moving ones repel.$\endgroup$
It’s an arbitrary choice, because the direction of $\vec B$ is not actually an observable.
Whenever you compute observables in electromagnetism — for instance, whether two parallel currents are attracted or repelled, or whether two skewed currents experience an aligning torque or an anti-aligning torque — you always find yourself using the right-hand rule an even number of times. For instance, you use the right-hand rule to find the direction of $\vec B$, then use the right-hand rule again to find the direction of $\vec v \times \vec B$. If you were to consistently use your left hand in every circumstance, you’d disagree with other people about the direction of $\vec B$, but you’d predict all of the same dynamics.
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Direction Associated With A Rotation
A different form of the right-hand rule, sometimes called the right-hand grip 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 grip rule is applicable.
This version of the rule is used in two complementary applications of Ampère’s circuital law:
The principle is also used to determine the direction of the torquevector. If you grip the imaginary axis of rotation of the rotational force so that your fingers point in the direction of the force, then the extended thumb points in the direction of the torque vector.
The right hand grip rule is a convention derived from the right-hand rule convention for vectors. When applying the rule to current in a straight wire for example, the direction of the magnetic field is a result of this convention and not an underlying physical phenomenon.
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