Back EMF (electromagnetic induction)

In summary: The difference in emf is what is used in the motor to convert electrical energy to kinetic energy. In summary, the current flowing through the coil of a motor causes it to spin, and this spinning motion creates a back EMF that opposes the change causing it. To maintain the same rotation rate, more energy needs to be supplied against this EMF, and this is the electrical energy that is converted to the kinetic energy of the motor. This energy comes from the battery or power supply supplying the motor.
  • #1
v_pino
169
0
1)When the current through the coil of a motor flows it cases the coil to spin.
2)The spinning motion causes the wires in the coil to cut through the magnetic field.
3)The current induced (back EMF) in the wires by this spinning motion opposes the change that causes it. (Lenz's Law)
4)Current supplied against this EMF requires electrical energy.
5)It is this energy that is converted to the kinetic energy of the motor.

I don't understand 4) and 5). Where does this electrical energy come from? I thought the motor's kinetic energy comes the the initial electrical current supplied to it...

Thanks.
 
Physics news on Phys.org
  • #2
I am a bit confused too but I think that:
Whenever a current carrying coil is put in a magnetic field, a torque acts on it. This is responsible for its rotational motion and forms the working principle of galvanometers.
But this rotational motion causes the induction of opposing emf and this tends to resist the rotation. So to keep up the same rotation rate more energy needs to be supplied. So it is this energy which gives the motor its kinetic energy.
 
  • #3
v_pino said:
1)When the current through the coil of a motor flows it cases the coil to spin.
2)The spinning motion causes the wires in the coil to cut through the magnetic field.
3)The current induced (back EMF) in the wires by this spinning motion opposes the change that causes it. (Lenz's Law)
4)Current supplied against this EMF requires electrical energy.
5)It is this energy that is converted to the kinetic energy of the motor.

I don't understand 4) and 5). Where does this electrical energy come from? I thought the motor's kinetic energy comes the the initial electrical current supplied to it...

Thanks.

The energy comes from the Battery or the power supply supplying the motor. The back emf generated is very small compared to the source emf.
 

1. What is Back EMF (electromagnetic induction)?

Back EMF, also known as counter-electromotive force, is a phenomenon that occurs in electrical circuits where a change in magnetic field induces a voltage in the opposite direction to the original current. This voltage opposes the original current and is known as back EMF.

2. How is Back EMF produced?

Back EMF is produced when the magnetic field around a conductor changes, either due to a change in current flow or a change in the position of the conductor in the magnetic field. This change in magnetic field induces a voltage in the opposite direction to the original current.

3. Why is Back EMF important in electrical circuits?

Back EMF is important in electrical circuits because it can cause damage to electronic components if not properly controlled. It can also affect the performance of motors and generators, as it counteracts the original current and can reduce the efficiency of the system.

4. How is Back EMF controlled in circuits?

Back EMF can be controlled in circuits by using components such as diodes, capacitors, and resistors. These components can dissipate or redirect the induced voltage, preventing it from damaging the circuit or affecting the performance of the system.

5. What are some real-world applications of Back EMF?

Back EMF has several real-world applications, such as in motors and generators. In motors, it can be used to control the speed and torque, while in generators it can be used to produce electricity. It is also important in devices such as speakers, where it allows for the conversion of electrical signals into sound waves.

Similar threads

Replies
11
Views
2K
  • Electromagnetism
Replies
16
Views
932
Replies
13
Views
2K
Replies
23
Views
956
Replies
50
Views
11K
  • Electromagnetism
Replies
9
Views
1K
Replies
10
Views
1K
  • Electromagnetism
Replies
1
Views
557
  • Electromagnetism
Replies
2
Views
4K
  • Electromagnetism
Replies
2
Views
1K
Back
Top