Table of Contents
Why does the current in an electric motor go down the faster the motor turns?
In an electric motor, current is passed through a coil in a magnetic field, so that a torque is exerted on the coil, and it starts to rotate. As the motor starts to spin faster, the back emf from the motor grows, reducing the current in the circuit.
When the back emf in a circuit is zero it draws how much current?
Back emf is the generator output of a motor, and so it is proportional to the motor’s angular velocity ω. It is zero when the motor is first turned on, meaning that the coil receives the full driving voltage and the motor draws maximum current when it is on but not turning.
What would happen to the coil if the current was too large?
If the current is too large, the heat loss can damage the circuit, burn the resistors, or even burn the surrounding objects.
How does current affect a motor?
The current through the motor times the resistance of the motor creates a small voltage that must be subtracted from the applied voltage. As the load and current increase, this IR drop also increases causing the motor to lose a little speed.
What happens to the back EMF when the motor turns faster?
As the motor turns faster, the back emf grows, always opposing the driving emf, and reduces both the voltage across the coil and the amount of current it draws. This effect is noticeable in many common situations.
What is the back emf of a coil?
The coil produces a back EMF (electromotive force) that is given by V= -L (di/dt). First of all, note that it is negative and secondly early in the process dt is small, so V will be a large number. Translated this means that you get a voltage spike at the coil terminal that is being driven by the electronics.
How does the direction of induced EMF affect current?
The direction of the induced EMF will control the direction of the induced current. The direction of the induced EMF follows from Lenz’s Law. Lenz’s Law. The current that is induced in a coil (due to a magnetic flux change through the coil) will always be such that it opposes the change that caused it.
What happens to magnetic flux when a coil is rotated?
When this generator coil is rotated through one-fourth of a revolution, the magnetic flux changes from its maximum to zero, inducing an emf. We recognize this situation as the same one in (Figure).