# When a wire is connected to 9 volt battery, the current is 0.020 ampere. What is the resistance of the wire?

pohnpei397 | College Teacher | (Level 3) Distinguished Educator

Posted on

In order to get the answer to this you must know the equation that gives you the relationship between voltage, current, and resistance.  That equation, which is derived from Ohm's law is

R = v/r

In this equation, I is the current (measured in amperes), v is the voltage, and r is the resistance.  Now that we know that, we can use the information that you have provided to solve this algebraically.

R = 9/.02

When you do the math here, you get 450

Resistance is measured in ohms so your resistance here is 450 ohms.

neela | High School Teacher | (Level 3) Valedictorian

Posted on

We know by Ohm's law that the current through a conductor is directly proportional to the voltage difference between its ends, provided the temperature and other physical conditions remain unaltered.

By the above , we mean V proprtional  to I

Or V = IR, where R is the constant of proportion and is also called the resistance of the conductor measured in ohms.

Therefore substituting the given values, V = 9 volt and  I = 0.020 A, we get:

9 v = (0.020 A)*R

R = 9/0.02 ohm.

Therefore the resistance of the conductor is 450 ohm .

R = 450 ohm.

giorgiana1976 | College Teacher | (Level 3) Valedictorian

Posted on

Any electrical device, including the wire, has the property called resistance.

The resistance could be calculate applying the formula:

R = dV/I (1)

dV = potential difference between the ends

I = the current in a given conductor

If a wire is connected to a battery, the amount of current in the wire depends on 2 aspects:

- potential difference provided by the battery

- the nature of the wire

We know, from enunciation, the potential difference of 9V andthe amount of current: 0.020A.

We'll substitute the values in (1):

R = 9V/0.020A

R = 450 Ohms