Question

if you plug a device that has a resistance of 15 ohms into a 120 V current, how much current does it draw?

Answer 1

Hint: Whenever a device conducts electricity, Ohm’s law can be applied in a circuit. If any two values involved in the formula of Ohm’s law are given, but one is not given, we can easily find the value by using the formula. For example, if the values of voltage and resistance are given but that of current is not given, we can find the value of current by using the Ohm’s law.

Complete answer:
The given data are resistance is equal to 15 ohms
And, current is equal to 120 V
Ohm’s law states that,
The voltage across a conductor is directly proportional to the current flowing through it, provided all of the physical conditions and temperature remain constant.
Voltage is the product of current and resistance.
In mathematical terms, the relationship between current and voltage can be expressed as,
\[V\text{ }=\text{ }I\text{ }R\]----(1)
Let this be equation (1)
Where,
V is the voltage
I is the current
R is the constant of proportionality known as resistance
From equation (1),
We get,
\[\text{ }I=\text{ }\dfrac{V}{R}\text{ }\]----(2)
Let this be equation (2)
Here,
\[V\text{ }=\text{ }120\text{ }V\]
And,
\[R\text{ }=\text{ }15\Omega \]
Substitute the value of V and R in equation (2)
We get,
  \[I=\dfrac{120}{15}\]---(3)
Let this be equation (3)
Solving equation (3),
We get,
The value of current as
\[I=8Amperes\]
Therefore, the answer is
\[I=8Amperes\]

Note:
Ohm’s law is applicable only in the case of conductors. Therefore, ohm’s law can be used in cases where the material conducts electricity. But, it is not applicable in case of insulators. That is, if the material used does not conduct electricity, Ohm’s law cannot be applied.