Series and parallel circuits

Question 1

what is a series circuit?

Answer 1

a complete circuit with more than 1 load and only one pathway.

Question 2

voltage law

Answer 2

total of all voltage drops is equal to the applied voltage. basically all the voltage is used.

Question 3

what is another name for voltage drop

Answer 3

IR drop because the voltage drop is equal to the amps*resistance

Question 4

its important to do what before measuring resistance?

Answer 4

disconnect the load from the circuit

Question 5

why measure voltage drop instead of resistance

Answer 5

1) you can only test resistance with a disconnected component and resistance changes with current.
2) voltage drop is dynamic, takes heat into consideration.

Question 6

what are some automotive applications of voltage drop

Answer 6

blower motor, dash lights

Question 7

Parallel circuits

Answer 7

a parallel circuit is a complete circuit with more than one path for the current to follow.

Question 8

does an open in one branch of a parallel circuit cause the other branches to stop working

Answer 8

no

Counterintuitively the resistance increases and the current will decrease. Its like the electricity knows what loads are ahead in the circuit and sends less current for less load.

1/Rt = 1/4 + 1/8 + 1/16
Rt = 2.28
I = 12/2.28
I = 5.26amps

1/Rt = 1/4 + 1/8
Rt = 2.66
I = 12/2.66
I = 4.51 amps

Question 9

parallel circuit law 1 current

Answer 9

not all of the current flows through each branch.

Question 10

parallel circut law 2 voltage

Answer 10

voltage is the same for each branch

Question 11

parallel circuit law 3

Answer 11

the sum of the current in each leg equals the total current

Question 12

how can you measure the total current in a parallel circuit?

Answer 12

treat each leg as a simple circuit. the total current is the sum of all the legs.

Question 13

the total resistance of a parallel circuit will be more/less than the smallest resistance in any leg?

Answer 13

less

Question 14

what is kirchoffs voltage law?

Answer 14

the total of all voltage drops is equal to applied voltage.

Question 15

what would current do if voltage was doubled in a circuit?

Answer 15

E=IR
I=E/R
6=12/2
12=24/2
current doubles

Question 16

what would current do if resistance was doubled in a circuit?

Answer 16

I=E/R
6=12/2
3=12/4
current would be halved

Question 17

What is the forumula for voltage drop?

Answer 17

Ohm’s law
E=IR

IR drop

Question 18

Why is the total resistance of a parallel circuit less than the smallest resistance?

Answer 18

1/Rt = 1/R1 + 1/R2
I don’t really get it. More answers here:https://physics.stackexchange.com/questions/269492/why-is-the-resistance-in-a-parallel-circuit-smaller-than-the-resistance-in-a-ser

Question 19

Why are parallel circuits used instead of series circuits in most automotive applications?

Answer 19

If one leg of a parallel circuit looses continuity the other legs will still work. Dont have a great understanding about this one, need to do more digging.

Question 20

Kirchoffs current law

Answer 20

the current flowing into a junction is the same as the current flowing out of a junction

Question 21

What would be the efect of an open circuit in one leg of a parallel portion of a series-parallel circuit?

Answer 21

only the leg with the open would be effected.

Question 22

What would be the effect of an open circuit in the series portion of a series-parallel circuit?

Answer 22

whole thing would stop working

Question 23

the amperage in a series circuit is the same or different ?

Answer 23

the same everywhere

Question 24

the sum of votage drops equals

Answer 24

applied voltage

Question 25

what is the formula for finding current

Answer 25

E=IR

I=E/R

Question 26

A series circuit has three reistsors of 4ohms each. The voltage drop across each resistor is 4v. Tech A says the source voltage is 12v. Tech B says the total resitance is 18ohms. Which is correct?

Answer 26

kirchoffs voltage law. the applied voltage is equal to the sum of all voltage drops. 4v*3=12v so source voltage is 12v. Total resistance in a series circuit is the sum of all resistances so the total resistance is 12ohms not 18. TECH A.

Question 27

a series circuit has two 10ohm bulbs. a third bulb is added in series. Tech A says that the three bulbs will be dimmer than when only two bulbs were in the circuit. Tech B says that the current will increase. Which tech is correct?

Answer 27

Three bulbs will be dimmer than two because there is more resistance to flow and therefore less current.

I=E/R

0. 6amps = 12v/20ohms
1. 4amps = 12v/30ohms

Question 28

Tech A says that the sum of the voltage drops in a series circuit should equal the source voltage. Tech B says that the current varies depending on the value of resitance in a series circuit.

Answer 28

Both techs are correct.

Kirchoffs voltage law states that applied voltage is equal to the sum of voltage drops. Therefore Tech A is correct.

Increased resistance decreases flow (current)
I=E/R
0.6amps = 12v/20ohms 
0.4amps = 12v/30ohms
Therefore Tech B is correct.

Question 29

Two bulbs are connected in parallel to a 12v battery. One has 6ohm resitance the other 2ohm resistance. Which bulb will be brighter?

Answer 29

Resistance decreases flow (current) and current is brightness. Therefore the 2ohm bulb will be brighter.

Question 30

Calculate the total resistance and current in a parallel circuit with three resistances, 4ohms, 8ohms, and 16ohms. Assume 12v?

Answer 30

1/Rt = 1/4 + 1/8 + 1/16
1/Rt = .4375
Rt = 1/.4375
Rt = 2.28ohms

E=IR
I=E/R
I=12/2.28
I = 5.26amps

Question 31

A vehicle has four parking lights in parallel, one of them blows. Tech A says that this could cause the fuse to blow. Tech B says that the current would decrease.

Answer 31

Increased resistance decreases flow (amps). Therefore current would increase. If current increased beyond the rating of the fuse the fuse could blow. Therefore Tech A is correct.

1/Rt = 1/2 + 1/2+ 1/2 +1/2
1/Rt = 2
Rt = 1/2
Rt = 0.5ohms

1/Rt = 1.5
Rt = 1/1.5
Rt = 0.6ohms