Understanding Back EMF: Effects on Parallel and Series Electrical Circuits

[moon2]

Ex:At home, you plug an electric drill into an electrical outlet and turn it on. At the moment you turn on the drill, the lights in the room(wired in parallel to the drill) flicker and dim briefly, but then return to normal after a moment.

notice that the example is wired in parallel, but in series lights will just get dim and stay the same.

what had happened in both of the case and how can i relate this to back emf?

 

[Meir Achuz]

When you turn the electric motor on, there is a surge of current, dimming other lights.
When the motor gets up to speed, there is a back EMF in the circuit which reduces the current through the motor.

 

[charng]

In both cases, the flickering and dimming of the lights is caused by the phenomenon known as back electromotive force (EMF). When an electric drill is turned on, it creates a magnetic field that induces a voltage in the wires of the circuit. This induced voltage, called back EMF, opposes the flow of current in the circuit and can cause fluctuations in the current and voltage levels.

In a parallel circuit, the lights and the electric drill are connected to the same power source, but they have separate branches. This means that the back EMF generated by the drill can affect the voltage in the light branch, causing the lights to flicker and dim briefly before returning to normal. In a series circuit, the lights and the electric drill are connected in a single loop, so the back EMF will affect the entire circuit, causing the lights to stay dim until the back EMF dissipates.

To relate this to back EMF, it is important to understand that back EMF is a result of the change in magnetic flux in a circuit. When the electric drill is turned on, it creates a changing magnetic field, which induces a back EMF in the circuit. This back EMF is proportional to the rate of change of the magnetic field and can affect the behavior of the circuit components, such as the lights in this example.

In summary, the flickering and dimming of lights in a parallel or series circuit when an electric drill is turned on is caused by the back EMF generated by the drill. This phenomenon is a result of the changing magnetic field created by the drill and can affect the voltage and current in the circuit. Understanding back EMF is crucial in designing and troubleshooting electrical circuits to ensure their proper functioning.