Magnetic Crane 1

[karalahana]

Hello I imagine such a circuit. I have a 5 amper circuit ad a 50 volt source voltage and this circuit feeds only a coil which lifts say a certain weight . Now what I wonder is what happens if I let the weight drop using my hand. Does the current keep on being 5 amper again or it decreases?

 

[VEBill]

In any steady state (with or without the [fixed] load), the only variable the affects the current is the DC resistance of the circuit.

 

[ScottyUK]

Depends if the source is AC or DC. VE1BLL's statement doesn't apply in the case of an AC source if the (presumably ferrous) weight being lifted completes the magnetic circuit and changes the reluctance of the magnetic path. For example, the current drawn by the coil of a magnetic contactor is considerably lower when the armature poles pull together than it is when it is in the open state.


----------------------------------

If we learn from our mistakes I'm getting a great education!

 

[VEBill]

Good point. I had assumed DC, but nothing in the OP supports my assumption.

 

[ScottyUK]

Nothing in the OP suggests you're wrong either!


----------------------------------

If we learn from our mistakes I'm getting a great education!

 

[karalahana]

Oh, in fact I had meant DC just to set the relation between the current and the holding force of an electromagnet in my head. It is for sure that as the force increases the current must increase but I think every current will create a force to hold a certain weight, but even if the weight is dropped the current in steady state will not change I guess, is it true in final stage of the words?

 

[VEBill]

A table can support a weight (applying a force) and requires no power. It's a mistake to think that a force necessarily requires power. Force over a distance would involve work, but a fixed-location force often doesn't.

 

[karalahana]

Yes I too think so. In fact I asked just to be sure of it. Thanks.