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I'm going to solve exercises from book page 143 that corresponds to the

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questions number four that some of you have been asking me first one it's to

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express this variable symbols so the first one is in millivolts remember that

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from that one millivolt it's equal to 0.001 volts so having to count this you only have to divide

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this figure by um 1000 so it's 0.037 volts next one um what you need to have into account is that

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one kilovolt it's equal to 1000 volts so here what you have to do is to multiply

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12 kilovolts by 1000 and here is exactly the same but be careful because 2.8 it's

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a decimal figure and the third one is exactly the same and in the first so the

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result is this one, 0.105 watts. Exercise 7 says that we have to indicate if they are in series

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parallel or in series parallel. Remember that they are in parallel if they are connected to

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the same points. For example, in this one, they are connected in this point and in this point,

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so a it's in parallel um the second b um remember that the definition i say uh circuit is in series

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if one device is after the other here we have three lamps they are connected one after the other

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so this one is in series the set the third one is exactly the same but they have put here this

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like MSC kit but it's in series and when you have one parallelism series and one

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parallelism combination is in parallel then this is a combination of series

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parallel here they are asking you to calculate the missing figure having in

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account the Ohm's law and I have explained this thing in class that you

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have the triangle of the Ohm's law V R and I here you can find it in the

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internet or just check your book so depending on the figure you need to

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calculate, you can guess the other figures. So let's calculate the

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resistance in this example. Resistance is voltage divided by intensity. Just take

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the figures 9 divided by 1. 9 volts divided by 1. The result is 9 ohms. So this is

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result in this exercise in the first one voltage it's equal to the intensity by the resistance

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intensity is in milliampere so transform it to one press okay and multiply it by the ohms by the

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resistance that is 100 1000 ohms and this result it's one volt in the second one you have to

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calculate the intensity the intensity is the voltage divided by the resistance so just take

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the figures that is 25 divided by 1 kilo ohm 1 kilo ohm is 1000 ohms so you have this result

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25 divided by 0.0 sorry 25 divided by 1000 that is us 0.00 sorry 0 25 amperes you can transform

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this measure to 25 milli amperes and this exercise is done in exercise number two it says that

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in a dcc kit with an involved battery it's providing a current of 0.03 amperes

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through a resistor calculate the resistance of the threshold resistors and um

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and do it in crocodiles and check the result okay we are going to do the first part the first part

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you have to take your own flow and calculate the resistor the resistance is equal to the voltage

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divided by the intensity and so it's 9 divided by 0.003 and plus take the calculator 9 divided

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by 0.003 it's 3 000 ohms and when it's set let's take the calculator clips and check your result

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it's three kilo ohms it's the same as three thousand ohms and here we have

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nine volts how we can check it we have two things to do just put your mouse

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over this and calculate the rhythm well it's not given I don't know why but

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there is another way to do it you can add a voltmeter no an

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ammeter here and this amateur is going to give me the result of three

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milliampers that is the one that was said in the in the in the exercise I

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take it and I paste it it said here draw a lamp with three lamps in series and a

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I have an R15V battery.

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In series means that one is after the other.

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These are the three lamps.

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And it said, R15V battery, it's here.

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And calculate intensity.

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We can measure it here, as I cannot do it.

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I put an ammeter, that is a device

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that measures the intensity.

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and it says 15 million price.

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This is the result.

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You can paste it here in the exercise.