# Chapter 19 Flashcards

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1
Q

Source of electromotive force

A

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

2
Q

EMF (ℰ) of the source:

A

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

3
Q

Is a battery a source of constant voltage or current?

A

Voltage

4
Q

Internal Resistance (r)

A

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

resulting in the generation of heat

5
Q

When is internal resistance more relevant?

A

With GREATER external resistance

6
Q

Terminal voltage

A

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

Vab = Va - Vb

7
Q

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

A

terminal voltage = emf

8
Q

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

A
9
Q

Circuit in series

A

connected end to end along a single path

10
Q

Resistors in SERIES

A
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

11
Q

Resistors in PARALLEL

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

total resistance < individual resistance

12
Q

Capacitors in SERIES

A

Net effect: LOWER capacitance

13
Q

Capacitors in PARALLEL

A

Net effect: HIGHER capacitance

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

14
Q

Kirchoff’s Junction Rule

A

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

15
Q

Kirchoff’s Loop Rule

A

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

V = 0

16
Q

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

A

Veq = V1 + V2 + … + Vn

17
Q

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

A

Veq = V1 – V2 – … – Vn

Electrons are forced into – terminal and removed from + terminal

Only works for rechargeable batteries (otherwise waste of energy)

18
Q

What are the pros of arranging batteries in parallel?

A

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)

19
Q

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

A
1. Heating tissue & causing burns
2. Stimulating nerves & muscles (shock)
20
Q

Ammeter

A

measure current (series)

Ideally 0 internal resistance

21
Q

Voltmeter

A

measure voltage (parallel)

Ideally HIGH internal resistance to DECREASE current

22
Q

Multimeter

A

measure voltage, current, resistance

23
Q

Ohmmeter

A

measure resistance (must contain battery of known resistance)

24
Q

Capacitor in circuit with no battery

Initially charged and now DISCHARGING

A
25
Q

Capacitor in circuit with no battery

Initially uncharged, now CHARGING

A