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Physics A-Level > Electric Current > Flashcards

Electric Current Flashcards

1
Q

What is current

A

Passage of charge particles

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2
Q

What is the conventional direction of current

A

From positive to negative

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3
Q

What is potential difference

A

Work done per unit charge

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4
Q

What is resistance

A

Voltage / Current

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5
Q

What is Ohm’s Law

A

Pd across a metallic conductor is proportional to the current through it

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6
Q

What is the unit for resistivity

A

Ohm metre

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7
Q

What is a superconductor

A

A wire made of material that has zero resistivity at and below a critical temperature

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8
Q

What are superconductor used for

A

Making high-power electromagnetic for very strong magnetic fields

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9
Q

What does a heater on a circuit look like

A

Four squares

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10
Q

What does an electric motor look like on a circuit

A

Circle with M in the middle, with line under it

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11
Q

Describe the I/V graph for a wire

A

y=x

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12
Q

Describe the I/V graph for a filament lamp

A

Slanted s

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13
Q

Describe the I/V graph for a diode

A

No current below 0 volts, then large peak after a few volts

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14
Q

When does resistance in a wire increase

A

When temperature increases, causing positive ions to vibrate more and stop charge carries from passing through

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15
Q

What are thermistors used for

A

Temperature sensors

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16
Q

How do thermistors work with increases temperature

A

Increased temp decreases resistance

17
Q

What is a potential divider

A

A combination of resistors in series connected across a voltage source to produce a required pd

18
Q

What is equation for energy dissipation per time

A

This is P = IV

19
Q

Define emf

A

Electrical energy produced over unit charge

20
Q

What is internal resistance

A

Resistance of materials within a battery

21
Q

What is the difference between emf and potential difference

A

Emf is energy converted from chemical to electrical.

Voltage is energy converted from electrical to other forms

22
Q

How to determine the emf and internal resistance of a battery

A

Measure V and I across a resistor, change R and repeat, draw graph of V vs I, emf is y-intercept and internal is negative gradient

23
Q

What is the equation involving emf

A

V = emf - Ir

24
Q

Why is measured voltage not equal to emf

A

Battery has internal resistance, current passes through this, work is done and volts are lost

Physics A-Level (19 decks)

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