Adam graduated from Virginia Tech in 2005 with a Bachelor's Degree in Technology Education. After college Adam began his teaching career at the Thomas Jefferson High School for Science and Technology. Adam currently teaches courses in Engineering and Energy Systems at TJ.
Basic Battery Circuitry
Engineer Adam Kemp discusses basic battery circuitry.
This expert: 1,168,444 views
Adam Kemp: Hi! I am Adam Kemp and today we are learning about how to make a battery. In this clip I am going to give an overview of how to light up an LED, a little bit of basic electronics and then finally how we are going to use our multimeter to measure all of the things we need to measure in our circuitry today. So to start off let's take a look at our LED. An LED, also known as a Light Emitting Diode, is a very low voltage, low current light source. The nice thing about an LED is that it uses low voltage and low current. You will find LEDs in places such as your computer monitor, which has an LED indicating the power and menu features. You also can see LEDs in the taillights of a lot of new vehicles and the nice thing about an LED is that it is very durable. It has an incredibly long light life and it also, like I said before uses a very little amount of power in order to illuminate. So the LED that we are working with today uses about 1.5 volts and about 20 milliamps of current. Now, let's learn about what we need to achieve those numbers using a potato, which is coming up in the next clip. There is two ways that we can connect our batteries together. The first way is called series. An orienting batteries is a series fashion is going to allow us to increase the voltage. So when we were talking about our LED, we require 1.5 volts in order to make the LED turn on and if we measure the voltage coming out of our first battery, which is going to be a potato battery it's going to be somewhere around .75 volts. So if we have got three potato batteries that are .75 volts, we can use the series orientation in order to increase their voltage, so that we can supply the proper amount of voltage to illuminate the LED. Now, each battery is going to have a positive side known as the anode and it's going to have a negative side called the cathode and the way we are going to connect these batteries together in series is we are going to connect the positives of the anode of one battery to the cathode of the other battery and what we are left with are one cathode and one anode and later when we connect our multimeter to the circuit, we'll see that the current flowing through the circuit is going to be the same, whereas the voltage is going to change and what it is gong to be is the sum of all the voltages . So if we talk about the voltage total, which we are trying to get somewhere above 1.5 volts, is going to be equal to the voltage coming out of the battery 1 added to the voltage coming out of the battery 2 and into the voltage coming out of the battery 3. So if we add the 3 voltages together we are going to end up with 2.25 volts. If we connect all three batteries in series, you will see that we get 2.25 volts and if we remember from before, the LED that we need to turn on only requires 1.5 volt. Now if we just give a quick look, we'll see that we can connect only two of these batteries in series and that would give us our 1.5 volts. Well, we don't want to discount this third battery we have because we might be able to use some of its resources. The way we are going to do that is using an orientation called parallel. If we take our batteries and start off with the three again, we can connect them in parallel to increase their current just like we did with series where we increased their voltage. Connecting batteries in parallel keeps them at the same voltage, but increases their current. So if we have again our batteries that are .75 volts and we connect them in parallel, where they have their anodes and cathodes and we connect them all together, we are left with two connections, one anode and one cathode and the product of this the total voltage is going to stay the same. Well, why would you want to connect them in this orientation? Well, each battery doesn't just have a voltage, it also has a current and that really comes into play when you are working with parallel circuitry. If the current coming out of our first battery was .05 milliamps, the current coming out of second battery would be .05 milliamps and the third battery is .05 milliamps and we need a total of 10 milliamps in order to drive our LED. We'll see that if we add those three currents up together, the total current is going to equal to .15 milliamps. The LED is going to require 1.5 volts at 10 milliamps. So this orientation wouldn't work because we only have .75 volts. So now let's talk about how we are going to light up this LED. If we remember from the beginning of this talk, the LED is going to need a voltage of 1.5 volts and current of 10 milliamps and if we look at our batteries, our batteries are going to be outputting about .75 volts and about .05 milliamps. So if we use our series in parallel circuitry, we can orient the batteries in such a fashion that we could achieve these numbers. So if we looked and we took two batteries that have .75 volts and we connected them together in series we would end up with the battery that is approximately 1.5 volts and .05 milliamps. Well, we have the voltage we need, but we don't have the current. Well, that's a good thing we made another battery because what we can do is now we can attach this final battery in parallel with this series circuit and we can increase that current from 5 to 10 milliamps. The way we are going to do that is we connect anodes together and the cathodes together and what we'll end up is a battery that is 1.5 volts .10 Milliamps. That is exactly what we need to in order to turn on our LED. Before we start building our batteries the final thing we need to do is understand how to use the multimeter. Now, what a multimeter is, it's a device that is going to allow us to measure the voltage and the current coming out of our batteries. At first glance, it is a relatively daunting looking piece of equipment, but once you get to understand its functionality, it's relatively easy to use. To start off, we are going to move our range selection wheel over into the direct current or D.C. voltage range. This is indicated usually by a large V followed by two lines; one of them is a solid line and other one is a dotted line and these indicate the anode and cathode that are found under direct current circuit. The range on this multimeter range anywhere from 600 volts D.C. all the way to 200 millivolts D.C. If you recall from the beginning of this clip, the batteries that we are going to be producing first are producing about .75 volts. So we can move our range selector down until the 2 volt range because .75 is a little bit less that 2, but much greater than 200 millivolts. This way we have a range that we'll be able to be measured by this multimeter. Coming up next, I am going to show you how to make a potato battery.