Does a resistor drop voltage, current or both?

Question

According to the voltage divider, a resistor reduces voltage, and i hear that current remains the same, in that case, why do we use a resistor to limit current?

Answer 1

Let's try it another way. A resistor is called that because it resists the flow of current. Electricity has to force its way through a resistor, and has to give up some energy to do it. The energy is turned into heat. Maybe only a little, maybe a lot. It depends on the value of the resistor and the amount of current. You could think of the resistor as a partial plug in a piece of pipe. Because the plug is there, the water current is reduced. It's the same with electricity. The electrical current is reduced.

If you measured the water pressure on both sides of a plug you would find that pressure was lost going through the plug. It's the same with electricity. The voltage (electrical pressure) is somewhat reduced.

No matter whether the resistor is by itself, in series with other resistors or in parallel with other resistors. The effect of this resistor is always to reduce voltage and reduce the current through itself.

Answer 2

A resistor drops voltage and limits current.

Voltage is dropped across any resistive part of a circuit. The total voltage drop equals the voltage source.

Current is limited by the value of the resistor. If the circuit has 10 volts applied and a 10 ohm resistor, the current is limited to 1 amp. If it has 10 volts and a 100 ohm resistor, current is limited to 0.10 amps, etc.

Answer 3

Given a constant voltage source, let's say 10 volts, the voltage at the source will always be 10 volts and the voltage at ground will always be 0 volts regardles of the amount of resistance in between.
Ohms law says the E/R = I. With a constant E, as R goes up, I goes down. For I to stay constant, R must stay constant.

A voltage divider is simply 2 or more resistors in series between the voltage source and ground with the ratio of the two resistors determining the voltage at their junction. Let's say you want the current to stay constant at 100 ma. Then the total resistance in the circuit needs to be 100 ohms. To change the divided voltage, simply change the value of the two resistors. If R1 is connected between the voltage source and R2 and R2 is connected between R1 and ground, then you could have the following pairs of resistors to give different voltages:
R1 R2 V
10 90 9
20 80 8
25 75 7.5
and so on.

If you make R1 = 100 ohms and R2 = 900 ohms then the divided voltage will still be 9v but the current has been reduce to 10ma.

Answer 4

If a current i flows through a resistor R there is a Voltage drop of

r*i
The current in a circuit of applied voltage V and equivalent resitance R is
I=V/R.
If you ad a resistor in adition to R of r Ohm the total current drops to i=V/(R+r) < I

Answer 5

Ohms law: (V)oltage = Current (I) x (R)esistance
To see how changes in resistor value affect current manipulate
V=IR to solve for I by dividing both sides by R
I= V/R At a constant voltage, say V=10, you can see that increasingly large value of R result in smaller values of I :
R=1 I=10
R=2 I=5
R=10 I=1

Answer 6

Won't it depend as to whether you're dealing with a parallel circuit or a series circuit?

Resistors will cause a change in the current in a parallel circuit, but the total never changes, more just goes through some resistors compared to others.

And to limit current, isn't that a safety issue.
It's not the potential (V) that kills a person, it's the amps

Answer 7

for no. 2 series RL E=sqroot(ER^2+EL^2)=sqroot(40^2+30^2)= =50V for no.1 current in the inductor=iL=E/XL=10/300=.0333A current in the resistor=iR=E/R=10/400=0.025A for parallel RL circuit lE=ER=EL for parallel circuits therefore voltage drop at resistor and inductor is=10V

Answer 8

That depends upon the circuit configuration:
http://en.wikipedia.org/wiki/Resistor#Series_and_parallel_circuits

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