Calculate the maximum current a 140 ohms, 1/2 watt

[Bobzombie]

I have looked thought all my notes and books and can not find the formal on how to do this question. I'm slowly going out of my mind any help would be great

Calculate the maximum current a 140 ohms, 1/2 watt resistor can have flowing through it safely.
Enter answer: mA

Then the 2nd part of the question is

What is the maximum e.m.f. which may be applied to the resistor above without causing overheating?

Enter Part 2 answer: V

 

[hotvette]

Don't you have some fundamental equations that relate voltage (V), resistance (R), current (I), and power (W)? You'll need them.

 

[quicknote]

To calculate the maximum current that can flow through a resistor, we can use Ohm's law, which states that current (I) is equal to voltage (V) divided by resistance (R). In this case, the resistance is 140 ohms and the power is 1/2 watt. To calculate the maximum current, we need to first convert watts to volts using the formula P=IV. So, 1/2 watt can be written as 1/2 volt-amp. Now, we can plug in the values into Ohm's law: I = (1/2 volt-amp) / 140 ohms. This gives us a maximum current of 0.00357 amps, or 3.57 milliamps (mA).

To answer the second part of the question, we need to use the formula P=IV again, but this time, we are solving for voltage. Since the power is 1/2 watt and the current is 0.00357 amps, we can write the equation as 1/2 = (0.00357)V. Solving for V, we get a maximum voltage of 140 volts. This means that we can safely apply a maximum of 140 volts to the resistor without causing it to overheat.