Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Physics H > Electricity > Flashcards

Electricity Flashcards

You may prefer our related Brainscape-certified flashcards:
Physics 101 flashcards AP® Physics flashcards
1
Q

What is alternative current a.c.?

A

changes its direction and instantaneous value with time

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is direct current d.c.?

A

The electrons flow in one direction only, and its value is constant

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is peak voltage equal to?

A

number of divisions x volts/divisions

(uses y gain ⬆️⬇️)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is period (T) of the wave equal to?

A

number of divisions x time per division

(uses time base⬅️➡️)

-> f=1/T

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are a.c. voltages stated in terms of?

A

Their r.m.s (root mean square) values-these are a kind of ‘average’ of the alternating ac supply

-ac readings on meters measure rms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the rms value of an ac supply equal to?

A

a dc supply which gives the same power output

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is current?

A

The dow of electric charge per second

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is potential difference?

A

the work energy required to move 1C of charge through an electric field

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what is supply voltage?

A

a measure of the energy given to electrons to make them move around the circuit

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is power

A

the energy transformed per second

The energy given to the electrons by the voltage supply is then transformed into other forms of energy by components

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Current rules

A

series
same at all points

parallel
add up to total

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

voltage rules

A

series
add up to supply

parallel
same at all points

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

resistance rules

A

series
add up to total

parallel
1/Rt = 1/R1 + 1/R2 + 1/R3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the e.m.f. (electromotive force) of a source?

A

The electrical energy supplied to each coulomb of charge which passes through the source

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is internal resistance? r

A

The resistance of the battery

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is lost volts?

A

the energy (per coulomb) that will be used up in overcoming the internal resistance of the supply

17
Q

What is the t.p.d. (terminal potential difference)?

A

The energy (per coulomb) left for the circuit (after energy is used for overcoming r).

The rod is the voltage obtained from a source of electrical energy when a current is being drawn from it.

18
Q

Situation: open circuit

A

switch is open (oof)/current is 0, voltmeter reading across supply will be emf

no current—>lost volts=0

19
Q

situation: under load (with an external resistance R)

A

The circuit is working normally->will be lost volts

emf=V+Ir

voltmeter reading across supply is tpd

20
Q

situation: short circuit (no external resistance)

A

All the energy from the battery is lost because of internal resistance

R=0
E=I(0+r)
E=Ir

The maximum current is the short-circuit current large enough to blow a fuse or circuit breaker

21
Q

Why does Vtpd decrease when current increases?

A

As current increases, the list colts increases (lost volts=Ir)
This means more energy is lost (per coulomb) as the electrons travel through the supply

If more voltage is lost across the supply, there will be less for the external circuit

Therefore, the rod will decrease (E=V+Ir

22
Q

What is a capacitor?

A

a component which stores electrical charge

consists of 2 conducting layers separated by an insulator
(simplest:2 metal plates with an air gap between them)

23
Q

What is capacitance measured in?

A

Farads F

The amount of charge that a capacitor can store depends on its capacitance

24
Q

What is a farad?

A

One farad of capacitance means that the capacitor can store one coulomb of charge per unit

25
Q

What happens as a capacitor is charging?

A

-pd across capacitor increases from 0 to the maximum value (supply V)

-the charging current decreases from an initial value of E/R to zero

-at all times the sum of the potential difference across the capacitor and the potential difference across the resistor equals the EMF of the supply

-the potential difference across the resistor decreases from an initial value of E to zero when the capacitor is fully charged

26
Q

What happens as a capacitor is discharging?

A

-The voltage decreases from the max (Vs) to 0

-the discharging current decreases from an initial value of -E/R to zero

-the potential difference across the capacitor is always equal to the potential difference across the resistor

-the potential difference across the resistor (given by ) decreases from an initial value of to zero when the capacitor is fully discharged

27
Q

Factors affecting the rate of charge and discharge?

A

-The resistance of the resistor (controls size of current)
-The capacitance of the capacitor (larger capacitances take longer to fill/empty)

SUPPLY VOLTAGE WILL NOT HAVE AN EFFECT

28
Q

How can you get a constant current while charging a capacitor?

A

Use a variable resistor

Current is constant —> Q=It

Physics H (5 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions