was looking at two simple circuits. The first had a 100 Voltbattery hooked acros
ID: 1664850 • Letter: W
Question
was looking at two simple circuits. The first had a 100 Voltbattery hooked across a 20 Ohm resistor. The second took that samebattery, unhooked it from the 20 Ohm resistor and hooked it up to a4 Ohm resistor.When I did this it thought that 100 divided by 20 is 5...so thatmeans this battery puts out 5 Amps of current. When I hook thatbattery up to the 4 Ohm resistor, the 5 Amps that flow through itwould give a potential difference of 5 times 4...20 Volts. BUT thisdoesnt equal 100. What am i doing wrong???
I'm aware that 100 Volts divided by 4 Ohms gives 25 Amps. The issueis how I'm thinking about the battery. What is am assuming abattery does? What does a battery really do (i.e. what does abattery really provide for the circuit?)
Explanation / Answer
Try not to think of the battery in terms of current when changingfrom one resistor to another. The battery provides thepotential to produce current. The number of electrons at eachpole of the battery is unequal. Once a resistor is connectedand the circuit is complete, current begins to flow. (Thereis actually some internal resistance that causes the battery toslowly degrade, but that is another discussion that doesn't applyto your problem) If you connected a wire with no resistanceto the battery, the current would approach infinity. Thebattery provides the ability to produce current, but it isdependent on the resistance of the circuit. The problem isthat you are thinking of the battery producing a constant amount ofcurrent. Current is not constant if you are changing theresistance of the circuit in a one resistor circuit. Thematerial of the resistor is limiting the potential to createcurrent. Going from 100 ohms to 4 ohms is a decent drop inresistance limitation. In your problem, the constants arevoltage and resistance, so the current must change. A lot ofpeople like to relate a circuit to the flow of water. Thebattery is a tap connected to a hose. The resistance is thehose. Changing the resistor is like changing the diameter ofthe hose. A large resistor is a smaller hose that allows lesswater to flow. The battery is the tap that is providing thesame amount of water, but changing the diameter of the hose changeshow much water can move through it-current. So the waterflow(current) is dependent on the amount of water available at thetap(voltage) and how much can flow through thehose(resistance).
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.