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Physics > Energy, Power, and Resistance > Flashcards

Energy, Power, and Resistance Flashcards

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1
Q

List three rules for drawing circut diagrams.

A

All wires and lines must connect to each other and componenets in the circle.

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2
Q

What is the difference between a cell and a battery?

A

A cell is a singular power house. A battery is multiple cells put together.

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3
Q

Define potential difference

A

The electrical potential energy converted to other forms per unit charge that flows. Measured in V.

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4
Q

Defune the volt. One volt is….

A

1 Volt = 1JC-1

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5
Q

What instrument is used to measure potential difference?

A

A voltmeter

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6
Q

Define electromotive force (e.m.f) in words.

A

The chemical/ source energy converted to electrical potetial energy per unit charge.

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7
Q

State the equation for e.m.f

A

E.m.f = W (Energy transferred by charge (Q)) over Charge (Q)

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8
Q

What is the difference between e.m.f and p.d

A

E.m.f is when work is being done on charge carriers. Charge carriers are gaining energy as they move through components.

P.d is when work is being done by the charge carriers. The charge is losing energy as they pass through components.

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9
Q

What is an electron gun? What can it be used for>

A

An electron gun is an electrical device used to produce a harrow beam of electrons. They can be used for particles by adding or removing electrons from atoms. It can also determine K.E

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10
Q

Describe how the beam of high speed electrons is produced after emission from the cathode.

A

Put inside a vaccum, high p.d is applied when the filament and anode. The filament acts as a cathode.

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11
Q

How is resistance deffined?

A

Resistance = P.D across component over Current in component.

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12
Q

What is the unit of resistance. How is it defined?

A

Ohm is defined as the resistance of a component when a p.d of 1V is produced per ampere of current.

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13
Q

State Ohm’s law

A

The current in an ohmic conductor is proportional to the p.d across the conductor provided the temperature is constant.

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14
Q

Explain why the resistance of a wire increases as it gets hotter.

A

The wire heats up over time which is caused by the current. The positive ions inside the wave have more internal energy and vibrate with greater apptitude.

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15
Q

What does an I-V characteristic of an electrical component show?

A

The relationship between electric current in a component and the p.d across it.

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16
Q

Explain the save of the I-V characteristic for the filament lamp.

A

Its not a stright line through the origin.

17
Q

What is a diode?

A

A diode is the component in a current that only allows to flow in one direction.

18
Q

What is the function of a thermistor?

A

At low temperatures, the resistance is high and the current can pass through.

19
Q

What does it mean if a thermistor has a negative temperature coefficent?

A

It means that instead of increasing resistance when the temperature increasesm these decrease the resistance.

20
Q

What is the function of an LDR?

A

To vary the resistance and current passing through depending on light levels.

21
Q

How does the resistances of an LDR change with light intensity?

A

The number density of charge carriers depending on light intensity.

22
Q

What type of material are themistors and LDRs made of?

A

Semiconductors.

23
Q

List 3 factors that affect the resistance of a wire.

A

The length, the material and cross sectional area of wire.

24
Q

How is resistance of a wire related to its length?

A

Resistance is proportional to the length.

25
Q

How is resistance of a wire related to cross-sectional area?

A

Resistance of a wire is inversely proportional.

26
Q

State the equation that can be used to calculate the resistance if you know the length cross-sectional area and restivity.

A

Restivity = Row (Restivity of materal) multiplied by Length over Cross sectional area.

27
Q

What are the units of restivity?

A

Ohm meters

28
Q

What is the difference between resistance and restivity?

A

Resistance is directly proportional to the length and temperature while it is inversely proportional to the cross-sectional area of the material. Resistivity is only proportional to the nature and temperature of the material. The SI unit of resistance is Ohms. The SI unit of resistivity is Ohms-meter.

29
Q

What is electrical power?

A

The energy transferred by each electrical component.

30
Q

What is the generic equation for power?

A

Power = Volt (p.d.) multiplied by Current

31
Q

Define kilowatt-hour

A

Kilowatt-hour is the energy transferred by a device for a time of 1 hour. The SI unit for energy is Joules.

Physics (8 decks)

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