Module 4 Chapter 1 Electricity: Charge and Current Flashcards

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1
Q

What two forms can the property ‘charge’ take?

A

Positive and negative.

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2
Q

What is the charge of an electron?

A

Negative.

1.6 * 10^-19 C

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3
Q

What unit is charge measured in?

A

Coulombs (C)

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4
Q

What is electrical current?

A

A flow of charged particles such as electrons or ions.

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5
Q

How can you calculate current based on charge?

A
I = ΔQ/Δt
current = change in charge / change in time
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6
Q

What carries the current in all metals?

A

Delocalised electrons.

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7
Q

What carries the current in electrolytes?

A

Dissolved ions.

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8
Q

What is Kirchhoff’s first law?

A

The sum of the currents entering a junction is equal to the sum of the currents exiting a junction.
This is also true for charge.

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9
Q

What does the conservation of charge mean?

A

Charge cannot be created or destroyed, only transferred. therefore, it is conserved.

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10
Q

How can you calculate charge based on current?

A
Q = I*t
charge = current * time
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11
Q

How can you calculate current using the charge of an electron?

A
I = n*e
current = number of electrons per second * the charge of an electron (1.6 * 10^-19 C)
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12
Q

How can you calculate charge over a period of time using the charge of an electron?

A
Q = n*e*t
charge = number of electrons per second * the charge of an electron (1.6 * 10^-19 C) * time in seconds
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13
Q

How do calculate mean electron drift velocity?

A
v = I/(n*A*e)
v = mean electron drift velocity
I = current
n = density of free electrons
A = cross-sectional area of the wire
e = the charge of an electron (1.6 * 10^-19 C)
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14
Q

How do you calculate current using electron drift velocity?

A
I = A*n*e*v
I = current
A = cross-sectional area of the wire
n = density of free electrons
e = the charge of an electron (1.6 * 10^-19 C)
v = mean electron drift velocity
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15
Q

What is the relationship between the density of free electrons in a material and its ability to conduct material.

A

The greater the density, the better an electrical conductor the material is.

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16
Q

What would be a typical density of free electrons in a conductor?

A

4.6 * 10^28 (calcium) to 1.8 * 10^29 (aluminium)

17
Q

What would be a typical density of free electrons in a semiconductor?

A

2.0 * 10^6 (gallium arsenide) to 2.0 * 10^13 (germanium)

18
Q

What would be a typical density of free electrons in an insulator?

A

close to zero.