Solving Current & Power Problems: Confused Beginner

In summary, the conversation covers problems related to current, power, and electric energy. The first problem involves calculating the charge and number of electrons flowing through a wire with a current of 1 ampere. The second problem involves determining the power and energy used by a lamp in a period of 5 minutes. Avogadro's number and the charge of an electron are mentioned as key concepts in the solutions. The conversation concludes with the individual gaining a better understanding of the concepts.
  • #1
exitwound
292
1
Problem 1

Just starting on the Current & Power chapter and I'm a little confused. I know they're just basic definitions and concepts, but I'm having trouble wrapping my head around it. Easy questions follow, but I'm lost.

Homework Statement



How many electrons flow past a point in a wire each second if the wire has a current of 1.00 Amperes?

Homework Equations



1 Ampere = 1 Coulomb/1 second
Avogadro's number = 6.02x10^23

The Attempt at a Solution



I don't know where to start.

Problem 2

Homework Statement


A lamp draws 0.50 A from a 120 V generator. (a) How much power does the generator deliver to the lamp? (b) How much electric energy does the lamp convert to light and heat in a period of 5.0 minutes?

Homework Equations



P=Energy/time or dU/dt or current*Voltage.

The Attempt at a Solution



a.) P=current*Voltage
P= (.5 Amps)(120 Volts)= 60 Watts

b.) I don't know where to start with this.

Maybe I'm just missing some key concepts, or something just isn't sticking in my stupid head due to the way it's been explained. I don't know.

Any help?
 
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  • #2
1) How much charge is flowing through the wire per second if the current is 1 ampere? What is the charge of an electron?

2b) The bulb converts electrical energy to light and heat, right? How much much energy does the bulb use in 5 mins?
 
  • #3
1.) I get the right answer if I divide 1/1.6e-19 but I'm not entirely sure why.

2b.) P=dU/dt
dU=P*dt
dU=60*300=18kJ which is right.

I didn't realize it said five MINUTES.
 
  • #4
Each electron has a fixed charge of -1.6e-19 C.
So with 1C/s it follows that there are

Units in brackets
electrons/second = 1 (C/s)/1.6e-19 (C) = 6.25E18 electrons per second.

It bit like saying a brick cost 25p, you have £1000 how many bricks can you get £1000/£0.25= 4000 bricks.
 
  • #5
Gotcha. As soon as I started reading your second sentence, it hit me. :)

Thanks guys. or girls. or dogs. or whatever you might be.
 
  • #6
None of the above I am actually a fish.
 

Related to Solving Current & Power Problems: Confused Beginner

1. What is the difference between current and power?

Current refers to the flow of electric charge, measured in amperes (A), while power refers to the rate at which energy is being transferred or used, measured in watts (W).

2. How do I calculate current and power?

Current can be calculated by dividing the amount of charge (in coulombs) by the time it takes to flow (in seconds), while power can be calculated by multiplying voltage (in volts) by current (in amperes).

3. What is Ohm's law and how is it used to solve current and power problems?

Ohm's law states that the current through a conductor between two points is directly proportional to the voltage across the two points, and inversely proportional to the resistance between them. This can be expressed as the equation V = IR, where V is voltage, I is current, and R is resistance. This equation can be used to solve for any of the three variables if the other two are known.

4. What is the difference between AC and DC current and how does it affect power calculations?

AC (alternating current) flows back and forth in a circuit, while DC (direct current) flows in one direction. AC is used for household electricity, while DC is used for batteries. When calculating power, the voltage and current values for AC are represented as RMS (root mean square) values, while for DC, they are represented as the actual values.

5. How can I troubleshoot issues with current and power in a circuit?

If the current or power values in a circuit are not what is expected, there may be a problem with the components or connections in the circuit. Using a multimeter, you can measure the voltage, current, and resistance at different points in the circuit to identify where the issue may be. Additionally, checking for loose connections, damaged components, or incorrect wiring can help troubleshoot the problem.

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