 In this video, we'll be looking at how to calculate the internal component resistor of an ammeter or the shunt resistor. Let me show you what I mean. When we're dealing with a meter, we're dealing with what's called a galvanometer. So it's this little fella right in here. This one has a full-scale deflection of 50 milliamps, meaning that when it sees its full current, the maximum you can see without getting broken, really, is 50 milliamps, and an internal resistance of 100 ohms. That's why I've got it circled and I've got the resistor drawn with the coil here. So this is our galvanometer. What we want to do is, if we're reading current, is make sure that this side here will never see more than 50 milliamps. That will be its maximum. So we need to get rid of the rest of the current going through there. If we're reading one amp or nine amps or 100 amps, we need to make sure that that 100 amps doesn't go across here. It needs to shunt across another resistor down here. So what we're going to do is learn how to calculate out what this resistor value is. So let's say that we're trying to read one amp. We know that our galvanometer here can only read 50 milliamps, so that means that we need to determine how much current is going to be going across this shunt resistor. Our first step to do that would be to calculate out 50 milliamps times 100 ohms using Ohm's Law means that we will be seeing 5 volts across this coil. So when we have full scale deflection, 50 milliamps flowing through here, we will see 5 volts. Once up, we're going to determine that this resistor down here will only see 0.95 amps, or 950 milliamps across this one. We did that by saying, okay, we know that we're trying to read one amp. We know that this has a full scale deflection of 50 milliamps, therefore the rest of it has to go across this resistor here. If you don't understand why that is, make sure you go watch the video on Kirchoff's Current Law, but our current needs to split off across these branches. So now we know that we have a 0.95 amps running across here when we have full value. We know that if we had 5 volts over here up top, we've got 5 volts here because they're in parallel, so the voltage remains the same again with Kirchoff's Voltage Law. So we have 5 volts here, 5 volts here, same voltage. If I have 5 volts and 950 milliamps or 0.95 amps, I can determine that my resistor value is 5.26 ohms just by using Ohm's Law. 5 divided by 0.95 gets us 5.26 ohms. Typically, these shunt resistors are going to be very small because you want to get the maximum amount of current through them, so they're going to be quite small in their size as opposed to a voltmeter resistor, which will end up being quite large.