Simple Electrical Equation Advice.

[MathsRetard09]

Homework Statement

Find the current in each resistor of a parrallel circuit.

R1 = 1kOhms
R2 = 1.5kOhms
R3 = 200Ohms

The voltage is 1800V

Homework Equations

IR1 = V / R1

IR2 = V /R2

IR3 = V / R3

The Attempt at a Solution

This is what I've done:

1800V / 1000ohms = 1.8mA = R1

1800V / 1500ohms = 1.2mA = R2

1800V / 200ohms = 9mA = R3

Is R3 supposed to be higher? I don't really understand electrical circuits and furthermore i appolagise if this is in the wrong topic.

 

[berkeman]

Homework Statement

Find the current in each resistor of a parrallel circuit.

R1 = 1kOhms
R2 = 1.5kOhms
R3 = 200Ohms

The voltage is 1800V

Homework Equations

IR1 = V / R1

IR2 = V /R2

IR3 = V / R3

The Attempt at a Solution

This is what I've done:

1800V / 1000ohms = 1.8mA = R1

1800V / 1500ohms = 1.2mA = R2

1800V / 200ohms = 9mA = R3

Is R3 supposed to be higher? I don't really understand electrical circuits and furthermore i appolagise if this is in the wrong topic.

Your general approach is correct, but you messed up a bit with the math and the labelling at the end.

1800V / 1000 Ohms = 1.8A, not 1.8mA. You have similar errors in the next two lines.

Also, the labels are not correct for the last 3 equations. The last 3 equations calculate I1, I2 and I3, not R1, R2 and R3.

 

[MathsRetard09]

Sorry i read this a while ago and forgot to thank you, yes that helped a lot. and thanks for moving it to a better location, i couldn't think cleary at the time. Thanks for your help.

 

[zgozvrm]

Is R3 supposed to be higher?

Yes. R3 is the lowest resistance.

Since all 3 resistors are in parallel, they all have the same voltage across them. You can therefore think of this as 3 separate circuits:
1) An 1800 volt source connected across a 1000 ohm resistor
2) An 1800 volt source connected across a 1500 ohm resistor
3) An 1800 volt source connected across a 200 ohm resistor

Now, think of these extreme cases:
1) The voltage source is not connected to anything. This is an open circuit. The resistance of the "circuit" is infinitely high and there is no current.
2) A piece of wire is connected across the terminals of the voltage source. This is a short circuit. The resistance of the circuit is very low (wire only), therefore the current is very high and either the voltage source or (more likely) the wire will burn up.


So, the answer is "yes." The R3 (the 200 ohm resistor) is the smallest load and has the highest current. This is reflected in Ohm's Law. E = I x R which, when rearranged becomes I = E/R. Dividing a number (E) by lower values (R), produces higher results (I). Conversely, dividing a number by higher values, produces lower results.