Chapter 19

Question 1

Source of electromotive force

Answer 1

device that transforms one type of energy → electric energy (ie. battery)

Question 2

EMF (ℰ) of the source:

Answer 2

potential diff (V) between terminals of device when no current flows to an external circuit

Question 3

Is a battery a source of constant voltage or current?

Answer 3

Voltage

Question 4

Internal Resistance (r)

Answer 4

opposition to the flow of current (I) from the cells/ batteries themselves

resulting in the generation of heat

Question 5

When is internal resistance more relevant?

Answer 5

With GREATER external resistance

Question 6

Terminal voltage

Answer 6

potential diff (V) across the terminals of a battery when the circuit is switched on

V_ab = V_a - V_b

Question 7

What is terminal voltage when no current is drawn from a battery?

Answer 7

terminal voltage = emf

Question 8

What is terminal voltage when current flows from a battery? EQUATION

Answer 8

Question 9

Circuit in series

Answer 9

connected end to end along a single path

Question 10

Resistors in SERIES

Answer 10

1. Charge has only 1 path to flow (current through each resistor same)
2. Charge loses energy as it passes through each resistor (voltage drop)
3. Sum of each voltage drop (V) = voltage of battery.

total resistance > individual resistance

Question 11

Resistors in PARALLEL

Answer 11

1. Charge has multiple paths to flow.
2. Voltage across each resistor = voltage of battery.

total resistance < individual resistance

Question 12

Capacitors in SERIES

Answer 12

Net effect: LOWER capacitance

Question 13

Capacitors in PARALLEL

Answer 13

Net effect: HIGHER capacitance

(essentially increasing area of the plates where charge can accumulate)

Question 14

Kirchoff’s Junction Rule

Answer 14

sum of all currents entering the junction = sum of all currents leaving the junction

Question 15

Kirchoff’s Loop Rule

Answer 15

sum of the changes in potential around any closed loop of a circuit = 0

V = 0

Question 16

When 2+ sources of EMF are arranged in series (normally)

Answer 16

V_eq = V₁ + V₂ + … + V_n

Question 17

When 2+ sources of EMF are arranged in series (opposite)

Answer 17

V_eq = V₁ – V₂ – … – V_n

Electrons are forced into – terminal and removed from + terminal

Only works for rechargeable batteries (otherwise waste of energy)

Question 18

What are the pros of arranging batteries in parallel?

Answer 18

Battery will go dead less quickly

Can provide more energy when more current is needed
Energy loss due to internal resistance LOWER (b/c each cell has to produce only a fraction of the current)

Question 19

Electric current through the human body can cause damage in 2 ways:

Answer 19

1. Heating tissue & causing burns
2. Stimulating nerves & muscles (shock)

Question 20

Ammeter

Answer 20

measure current (series)

Ideally 0 internal resistance

Question 21

Voltmeter

Answer 21

measure voltage (parallel)

Ideally HIGH internal resistance to DECREASE current

Question 22

Multimeter

Answer 22

measure voltage, current, resistance

Question 23

Ohmmeter

Answer 23

measure resistance (must contain battery of known resistance)

Question 24

Capacitor in circuit with no battery

Initially charged and now DISCHARGING

Answer 24

Question 25

Capacitor in circuit with no battery

Initially uncharged, now CHARGING

Answer 25