I am having a hard time understanding this please help! Electricity and magnetism?

Question

Rearrange the equation current=voltage/resistance to express resistace in terms of current and voltage. Then solve for the following: A certain device in a 120-V circuit has a current rating of 20 A. What is the resistance of the devise (how many ohms)?

The wattage marked on a lightbulb is not an inherant property of the bulb but depends on the voltage to which its connected, usually 1110 or 120 V. How many amperes flow through a 60-W bulb connected in a 120-V circuit?

Answer 1

The answer to your first question requires only simple algebra. Why can't you solve it?

The second part of your question can be solved using the equation, P = I x V, where P is the watage, I is the current, and V is the voltage.

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I shouldn't be doing your homework for you, but here it is:

1) If I = V/R (what you are given)
then R = V/I

So, R = 120/20 = 6 ohms

2) P = V x I, so I = P/V

I = 60/120 = 1/2 amp

Answer 2

Question #1:

Current = Voltage / Resistance

Or, the way it is more typically written,

I = V/R (where I = current, V=voltage, R=resistance)

Multiplying through by R

R*I = V

Now, divide through by I

R = V / I There ya go, resistance in terms of voltage and current

Now fill in the numbers and solve for R
V = 120 volts
I = 20 amps

R = 120 / 20 = 6 ohms

Question #2:
The equation for power is

P = V * I

Rearranging in terms of current,
I = P / V

Now, plug in the numbers from the problem above
P = 60 watts
V = 120 volts

So, I = 60/120 = 0.5 amp

Hope this helps,

-Guru

Answer 3

just remember: V=IR where V= voltage, I = current, & R= resistance.

So R in terms of V and I is: R = V/I

therefore: 120-V/ 20 A = 6 ohms

watts are measured by power P and P = VI
so using this equation you will get:

60 W = 120-V * I
to get I, divide 60 by 120. So your you will get 1/2 A.

Answer 4

question #a million: contemporary = Voltage / Resistance Or, the way this is greater usually written, I = V/R (wherein I = contemporary, V=voltage, R=resistance) Multiplying via way of via way of R R*I = V Now, divide via way of via way of I R = V / I There ya bypass, resistance in words of voltage and contemporary Now fill in the numbers and make sure for R V = one hundred twenty volts I = 20 amps R = one hundred twenty / 20 = 6 ohms question #2: The equation for power is P = V * I Rearranging in words of contemporary, I = P / V Now, plug in the numbers from the impediment above P = 60 watts V = one hundred twenty volts So, I = 60/one hundred twenty = 0.5 amp desire this is helping, -Guru

Answer 5

"E" means electromotive force, or Volts.
"I" means current
"R" is resistance
Watts is the unit of Power, which is usually "P".
P=I^2xR or E x I
Watts is also expressed as Volt amps, or VA
P = E x I, so
60VoltAmps = 120V x 'I' amps
'I' = 60VA/120V
I = .5 amps
We'll leave the RMS theory out for now.

Answer 6

R = E / I
E = R x I
I = E / R

P = E x I
P = E^2 / R
P = I^2 x R

Answer 7

huh?