easy electromagnet/simple circuits questions?

Question

in a series circuit, what would be the current and power if the battery is 1.5 V and the bulbs have a resistance of .5? what about a parallel circuit?

does any part of a circuit (for an electromagnet) have a resistance? if so, what is it? what item in your house may be wired the same as an electromagnet?

Answer 1

how many bulbs?
I will assume 2 bulbs just to show the calculation.
in series, the bulbs both resist a single path of current, so
current = 1.5v / (.5 + .5)

In paralel the bulbs each offer a path for current to flow. so the total current should be higher.
current = 1.5v / [ 1/(1/.5 + 1/.5)]

in a true electromagent the wire has a tiny tiny amount of resistance. this is usually ignored in school calculations.
Also a battery has an 'internal resistance'. this a way to describe how as you ask for more current from a battery the voltage drops. depending on your class they may consider this, or not.

The traditional example of an elctromagnet in the home is the door bell. when you push the button you energize an electromagnet that moves a rod to make the 'ding' and when you let go the rod moves back to make the 'dong'

Answer 2

For N bulbs

series
I = V / ( N*R )

parallel
I = V / ( R / N )

i is current ; V is voltage (1.5) ; R is resistance (0.5)

The wire of an electromagnet does have resistance. The resistance can be quite significant if the wire is very thin and long (with a large number of turns). The magnetic field strenth increases with current but it also increases with a larger number of turns of wire.

The speakers used in your computer speakers, television, radio will all have a electro magnet voice coil. http://en.wikipedia.org/wiki/Speakers#Driver_design

Motors contain electro magnets (fans, washing machine, dryer, dishwasher...).
http://en.wikipedia.org/wiki/Electric_motor

Solenoid valves used in clothes washers and dishwashers use electromagnets.
http://en.wikipedia.org/wiki/Solenoid_Valve


Electromagnets used to be used in a lot of applications. In some cases electronics or piezoelectric devices have replaced electromagnets.
http://en.wikipedia.org/wiki/Piezoelectricity

Fewer relays are now used as they have been replace by solid state devices in many cases.