Units and formulas Flashcards

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1
Q

Frequency is measured in what unit? What is the formula for frequency?

A

hertz(Hz)

s-1

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2
Q

Force is measured in what unit? What is the formula for force?

A

Newton, N

kg * m/s2

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3
Q

Energy/work is measured in what unit? What is the formula for energy/work?

A

Joules (j)

N*m

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4
Q

Power is measured in what unit? What is the formula for power?

A

Watts (W)

J/s

also

P = Vi (voltage*current)

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5
Q

Electric charge is measured in what unit? What is the formula for electric charge?

A

Coulomb (C)

A*s

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6
Q

Electric potential is measured in what unit? What is the formula for electric potential?

A

Volts (V)

J/C

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7
Q

Electric resistance is measured in what unit? What is the formula for electric resistance?

A

ohm(Ω)

V/A

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8
Q

Electric conductance is measured in what unit? What is the formula for electric conductance?

A

siemens(S) - mathematical symbol is G

A/V

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9
Q

What do the following letters symbolise?

V =

W =

q & Q =

i =

t =

P =

A

V = voltage in volts

W = the energy (work) in joules

q & Q = the charge in Coulombs (intantaneous - q) (static charge - Q)

i = current measured in Amps

t = time in s

P = power measured in Watts

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10
Q

What is the difference beteween positive and negative power?

A

Energy that is dissipated (lost) is considered positive.

e.g. a 60W lightbulb dissipates that energy, but is considered a positive wattage.

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11
Q

What is the equation for voltage (V)?

A

V = iR

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12
Q

What is the equation for current (i)?

A

i = V/R

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13
Q

What is the equation for Power (W)?

A

W = iV

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14
Q

What is the equation for Resistance (Ω - ohms)?

A

Ω = V/A

or

Ω = pl / A

where p = resistivity of the material

l = length of the material

A = area (cross sectional area)

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15
Q

If V = iR and P = iV, how else could P be calculated in relation to R?

A

V = iR

P = iV

so

P =i*(iR) = i2R = V2/R

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16
Q

What is the scientific notation for:
Tera
Giga
Mega
Kilo

A

1012

109

106

103

17
Q

1 electron is equal to how many Coulombs?

1 Coulomb is equal to how many electrons?

A

1e = 1.602*10-19 C

1C = 6.242*1018e