Chapter 10: Electrical Circuits

Question 1

What is Kirchhoff’s Second law

Answer 1

For any path (loop) of a circuit, the sum of all the potential differences must equal the total emf of the circuit

Question 2

How do you find the total resistance in a series circuit?

Answer 2

R1 + R2 + R3…

Question 3

How do you find the total resistance in a parallel circuit?

Answer 3

1/R1 + 1/R2 + 1/R3…

Question 4

Does adding a resistor to a circuit in parallel always reduce the total resistance?

Answer 4

Yes

Question 5

How can you measure current in a circuit?

Answer 5

Ammeter connected in series to a component

Question 6

How do you measure the potential difference of a component

Answer 6

voltmeter connected in parallel over the component being measured

Question 7

In a parallel circuit, is the total voltage in each loop the same?

Answer 7

yes

Question 8

How do you calculate the total voltage in a series circuit?

Answer 8

V1 + V2 + V3…

Question 9

How does the current vary between each component of a series circuit?

Answer 9

current remains the same throughout the circuit

Question 10

Is the current in each component of a parallel circuit the same?

Answer 10

No.
Each branch has a different current
Voltage across each branch is the same - the higher the resistance the lower the current flow

Question 11

If two cells are connected in series, with positive terminal to positive terminal, what will be the total EMF?

Answer 11

ϵ1 + ϵ2

Question 12

In a series circuit, if the cells are connected negative to negative, what would be the total emf be

Answer 12

ϵ1 - ϵ2
The EMFs would cancel out

Question 13

Would the EMF of a source and its terminal voltage be the same?

Answer 13

No.
Not all the energy given to the charges in the course makes it out of the cell

Question 14

Internal Resistance

Answer 14

the resistance within a power source due to the materials and components which make it up

Question 15

What are ‘lost volts’

Answer 15

The difference in voltage between that supplied by the source and the amount available in the circuit.
They are ‘lost’ due to the internal resistance of the source

Question 16

What is the equation relating e.m.f to total load and internal resistance

Answer 16

ϵ = I(R + r)
R = load resistance
r = internal resistance
ϵ = V + v
V = voltage used in circuit (terminal voltage)
v = lost volts

Question 17

terminal voltage

Answer 17

voltage used in circuit after lost volts reduced from the e.m.f

Question 18

Experiment to determine the internal resistance of a source

Answer 18

1) Set up circuit with a source, ammeter, voltmeter and variable resistor
2) Vary the resistance and measure V and I
3) Plot a V-I graph
4) V = -rI + ϵ -> V = mx +c
5) internal resistance = (-)gradient

Question 19

What is the purpose of a potential divider?

Answer 19

To provide variable potential difference, or to provide a constant specific potential difference

Question 20

How does the voltage across a component in a potential divider correspond to its resistance?

Answer 20

ratio of V to Vt = ratio of R to Rt
they are directly proportional

Question 21

How can a potential divider circuit be used as a sensing circuit?

Answer 21

1) Put a resistor that varies with the desired conditions in a potential divider
2) Insert the responding load over either the variable resistor or fixed, depends on how circuit should work

Question 22

How do you vary Voltage out in a potential divider circuit?

Answer 22

switch one of the resistors for a variable resistor

Question 23

EMF Definiton

Answer 23

the energy per unit charge which is transferred from chemical to electrical energy

Question 24

PD Definition

Answer 24

the energy per unit charge which is transferred from electrical to other forms

Question 25

How to calculate the EMF of a circuit?

Answer 25

ϵ = I(R + r)
1) Measure terminal PD at different currents
Extrapolate the line back to the Y axis (terminal PD)