What is a Magnet?
Magnet is a device/object that produces an external magnetic field. It applies force over other magnets, charges, electrical current, and magnetic material. There are several types of magnets. Permanent magnets are the ones which do not lose their magnetism. The majority of the magnets you see are man-made around you. Since they were not initially magnetic, they have lost their magnetic properties over time. For example, dropping them weakens their magnetism. Most of the man-made magnets were originally non-magnetic, and so they lose their magnetic character with time.
What is a Magnetic Field?
The magnetic field is an invisible field around a magnet or magnetic object, in which magnetic force is exerted. The invisible area around a magnetic object can pull up another magnetic object or push away another magnetic object. Moving electric charge generates magnetic fields. A magnetic field can be produced when electrons, which have a negative charge, move about in some certain direction. Magnetic fields can be represented by the continuous line of forces that emerge from the north pole of the magnet and enter into the south pole of the magnet and vice-versa inside the magnet. The density of the lines shows the magnitude of the magnetic field at any point.
Mathematically, the magnetic field can be defined in terms of the amount of force exerted on a moving charge in a magnetic field. This force can be measured with the help of Lorentz Force law,
F = qvB
Where,
F-Force exerted on the moving charge
q-the amount of charge
v-velocity of the moving charge
B-Magnitude of the magnetic field
Here, this relationship is a vector product, and the force is perpendicular to all other values.
Effect of Magnetic Field on a Current-Carrying Wire
Electric energy is transmitted by the current, which is basically the flow of the electrons, which are the sub-particles of the atom and are negatively charged. This movement of electrons from one location to another power our lights, computers, appliances, and many other things. Another fascinating fact about electric current is that it produces its own magnetic field. Magnetism and electricity have a close relation in that all closed-loop currents generate their own magnetic fields, and magnetic fields acting on closed-loop circuits may produce current. The magnetic effect of electric current was discovered by Oersted.
Experiment: How Magnetic Field Affects Current-Carrying Wire?
Materials
Strong horseshoe magnet
Wire stripper
Long insulated wire
Electrical tape
D battery
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Procedure
Remove 1 inch of insulation of the wire from each side.
Place the horseshoe magnet onto a flat surface on its side.
Using a tiny piece of electrical tape to tape the metal portion of one end of the wire through the battery's negative terminal.
Move the horseshoe magnet wire between the legs.
Holding the insulated portion of the wire, connect the wire's open end to the positive battery terminal. What direction is the movement of the electric current? Why do you have to maintain wire insulation instead of metal? List your findings.
Flip over the magnet and repeat the procedure. How, if anything, will change? Document your thoughts.
Results
The wire would bend away from the magnet's poles.
Why this Happens
As we know, electric currents always produce their own magnetic fields. The behavior and the direction of the current can always be described by the right-hand rule. Simply point your thumb towards the direction of current flow, and curl your fingers around the wire, the direction of the curl fingers will give the direction of the magnetic field as shown below in the figure.
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That means you also change the direction of the magnetic field when you change the direction of the current. Magnets have two poles, South and North, like the horseshoe magnet used in this exercise. The term 'attracting opposites' refers to magnets; thus, interactions between north and south hold together, and interactions between north and north and south and south repel or move away from each other.
Fun Facts
The north pole and south pole of a magnet cannot be separated. Cutting one magnet in half makes two magnets, with two poles each.
Earth’s magnetic field is around 1,000 times weaker than the typical bar magnet.
Cranes use huge electromagnets to pick up scrap metal in junkyards.
Electromagnets use electricity to generate their magnetic power. When the electricity is turned on and off, the magnetic power can be turned on and off.
If you attach a bar magnet to a piece of wood and place it in a water bath, it will gradually turn into the water until the North Pole of the magnet points towards the North Pole of our planet. Temporary magnets are used to do the same.
FAQs on Effect of Magnetic Field on Current Carrying Wire
1. What happens when a current-carrying wire is placed in a magnetic field?
When a wire carrying an electric current is placed within an external magnetic field, it experiences a mechanical force. This phenomenon is often called the 'motor effect'. The force arises from the interaction between the external magnetic field and the magnetic field produced by the moving electric charges (the current) within the wire. The wire will be pushed or pulled, and the direction of this movement depends on the direction of both the current and the magnetic field.
2. Why does a current-carrying wire experience a force in a magnetic field?
The force on the wire is the collective result of the force acting on individual moving charges within it. An electric current is essentially a flow of charged particles (electrons). According to the principles of electromagnetism, any single moving charge experiences a force (known as the Lorentz force) when it travels through a magnetic field. Since the wire contains billions of these moving electrons, the small forces on each electron add up to a significant, observable macroscopic force on the wire itself.
3. How is the force on a current-carrying wire in a magnetic field calculated?
The magnitude of the force (F) on a straight current-carrying wire in a uniform magnetic field is calculated using the formula: F = BILsinθ. Here is what each variable represents:
- F is the magnitude of the force, measured in Newtons (N).
- B is the strength of the magnetic field, measured in Tesla (T).
- I is the magnitude of the electric current, measured in Amperes (A).
- L is the length of the wire that is inside the magnetic field, measured in meters (m).
- θ (theta) is the angle between the direction of the current and the direction of the magnetic field.
4. How can you determine the direction of the force on a current-carrying wire?
The direction of the force can be determined using Fleming's Left-Hand Rule. To apply this rule, you arrange your thumb, forefinger, and middle finger of your left hand so they are mutually perpendicular to each other.
- The Forefinger points in the direction of the Magnetic Field (B).
- The Middle finger points in the direction of the Current (I).
- The Thumb will then point in the direction of the resulting Force (F) or thrust on the conductor.
5. What factors affect the strength of the force on the wire, and when is this force maximum?
The strength of the force is determined by four main factors, as seen in the formula F = BILsinθ: the magnetic field strength (B), the current (I), the length of the wire in the field (L), and the angle (θ). The force is at its maximum when the wire is positioned perpendicular (at 90°) to the magnetic field, because sin(90°) = 1. The force is zero when the wire is parallel to the magnetic field, because sin(0°) = 0, meaning there is no interaction force.
6. What is a practical, real-world application of this force on a current-carrying wire?
The most common and important application of this principle is the electric motor. In a motor, a coil of wire carrying a current is placed in a magnetic field. The force on opposite sides of the coil acts in opposite directions, creating a turning effect or torque. This torque causes the coil to rotate continuously, converting electrical energy into mechanical energy. This is the working principle behind devices like fans, washing machines, mixers, and electric vehicles.
7. What is the difference between the magnetic field *produced by* a wire and the force it *experiences* in a field?
This is a crucial distinction.
- Producing a Field: Any wire carrying a current generates its own magnetic field around it. This is known as Oersted's discovery. The shape of this field is a series of concentric circles around the wire, and its direction can be found using the Right-Hand Thumb Rule.
- Experiencing a Force: A force is experienced only when this wire (which is already generating its own field) is placed inside an external magnetic field from another source (like a permanent magnet). The force is the result of the interaction between these two fields. The direction of this force is found using Fleming's Left-Hand Rule.
8. Can two parallel wires carrying current exert a force on each other?
Yes, they can and they do. Each wire creates its own magnetic field, and the other wire is situated within that field, thus experiencing a force. The outcome depends on the direction of the currents:
- If the currents in both wires flow in the same direction, the wires will attract each other.
- If the currents flow in opposite directions, the wires will repel each other.
