Resistors in Series and Parallel

Question 1

if you had three resistors in series and you could measure the current in between each of them, what would you observe

Answer 1

the current would be the same at every part

Question 2

why would the current be the same, simply put

Answer 2

because of the conservation of charge

Question 3

what does the conservation of charge state

Answer 3

• the rate at which electrons leave each component must be the same as the rate in which they enter
• as there is nowhere else for them to go

Question 4

if you put a voltmeter across all of the resistors at once, then more in between the first, second and third resistor, what relationship would all of the those potential differences have

Answer 4

• the first pd reading equals the sum of all the three other readings
• V = V1 + V2 + V3

Question 5

how would the equation change if you substituted V for the products of its equation

Answer 5

IR = IR1 + IR2 + IR3

Question 6

how would you use that equation to prove that resistance of resistors in series add up to make a larger sum of a resistance across the whole circuit

Answer 6

• cancel out the current
• leaving you with R = R1 + R2 + R3
• therefore, the resistance across the whole circuit is equal to the sum of each of the resistances the resistors supply

Question 7

how is the conservation of charge at a junction, lets say with three different routes, written out in an equation

Answer 7

I = I1 + I2 + 13

- where I is the total current and the others are at the three different routes

Question 8

if you have a resistor in each route, and I = V / R, how can you rewrite that equation to show the resistance in this circuit

Answer 8

V / R = V / R1 + V / R2 + V / R3

Question 9

how does the potential difference change when it meets a junction and enters different routes

Answer 9

• it doesnt change

- the potential difference is the same in all routes as well as in series

Question 10

what could you therefore call V in the equation and how would it be written out

Answer 10

• it could be 1

- giving you 1 / R = 1 / R1 + 1 / R2 + 1 / R3

Question 11

what does this overall mean about how the resistance changes in series and in parallel

Answer 11

• the resistance increases when in series

- but the resistance decreases in parallel