How will a current change if the voltage in a circuit is held constant while the resistance doubles? 1. it's impossible to predict. 2. the current will drop to half of its original value. 3. the current will triple. 4. the current will remain the same. 5. the current will double?

According to Ohm's Law: 



Where: V = Voltage
            I = Current
            R = Resistance

As you can see here, you can say that Current is directly proportional to Voltage and indirectly proportional to Resistance. This means that as the voltage increases, current increases and as the resistance increases, current decreases. 

So in your scenario, if the voltage remains the same, but the resistance is doubled, that means that the current will be halved. So the answer to your question is 2. the current will drop to half of its original value.