Relationship between current and voltage and resistance
Physics Narrative for 11-14
Relating voltage, current and resistance
Setting up a simple circuit consists of selecting two components – the battery and the bulb, and linking them with wires. The two choices you make set the
push: the voltage of the battery, and how much that push is impeded: the resistance of the bulb. The current in the loop is the result of these two choices. Much more on this in the SPT: Electricity and energy topic.
The relationship between the push of the battery and the size of electric current is summarised by:
current = voltageresistance
You can write this out in symbols:
I = VR
Where V is voltage, measured in volt; I is current, measured in ampere; R is resistance, measured in ohm.
According to this relationship, if the resistance does not change, then increasing the voltage results in an increase in current.
Choosing a 3 volt battery and a 10 ohm resistor results in a current of 0.3 ampere in the resistor (and in the battery, and in the connecting wires).
I = VR
Put in the values to get:
current in loop = 3 volt10 ohm
and work out the current as 0.3 ampere.
If the battery voltage is doubled to 6 volt, the new current is still given by I = VR, but you need to insert the new values current in loop now = 6 volt10 ohm and calulate the current as 0.6 ampere.
There is a 0.6 ampere current in each part of the circuit loop: in the lamp; in the battery; in both the connecting wires.
Double the battery voltage gives double the current.