Question

you have a toy car running on two batteries. if you could hook it up wit only one of the batteries, it would draw

a)twice as much current as the two batteries

b) half as much current as the two batteries

c) the same amount of current as the two batteries

why??

Answer 1

c) the same amount of current as the two batteries

Current in a DC circuit follows Ohm's law, V = I*R which says that the voltage "V" applied across a load equals the current "I" in amps multiplied by the resistance "R" of the load in Ohms.

Batteries can be connected in series, where the voltages add and the capacity is the same as that of a single battery, or in parallel, where the capacities add but the voltage stays the same. In series connection, the negative of one battery is connected to the positive of another. In a parallel connection, the positive connects to the positive and the negative to the negative. You can Google diagrams for series and parallel connections...I think the pictures make it a lot more obvious what the differences are between them.

If you removed a battery and the current did not change, then they must have been connected in parallel. If the resistance of the load did not change, then the only way the current would change is if the voltage from the battery changed. Since it did not change, then you must have had the batteries wired in parallel. If they had been in series, removing one would reduce the voltage (and, by Ohm's law, the current) by half.