Phase Difference

Thread Starter

EYT1

Joined Apr 7, 2020
84
There is a 90 degree phase difference between the currents whose effective values are Ief1 = 3 amperes and Ief2 = 4 amperes. Approximately how many amperes are the total values of the currents in vector?


can you help me how to solve it
 
Last edited:

OBW0549

Joined Mar 2, 2015
3,459
Good grief. This problem is so easy it's trivial; any high school sophomore should be able to solve it.

The two currents are 90° apart; that is, they are at right angles to one another. What do the two vectors form if you connect their ends together? Have you ever heard of a right triangle? Have you ever heard of the Pythagorean Theorem?

If the above doesn't give you enough hints-- along with the hints in the original question-- to easily solve the problem yourself, you're probably hopelessly lost.
 

Thread Starter

EYT1

Joined Apr 7, 2020
84
Good grief. This problem is so easy it's trivial; any high school sophomore should be able to solve it.

The two currents are 90° apart; that is, they are at right angles to one another. What do the two vectors form if you connect their ends together? Have you ever heard of a right triangle? Have you ever heard of the Pythagorean Theorem?

If the above doesn't give you enough hints-- along with the hints in the original question-- to easily solve the problem yourself, you're probably hopelessly lost.
A^2 +B^2=C^2
 

OBW0549

Joined Mar 2, 2015
3,459
Correct.

Specifically, 5 amps is the amplitude (the absolute value, or magnitude) of the resulting current when currents A and B are added. The Pythagorean Theorem works because the currents A and B are orthogonal-- that is, they're 90 degrees out of phase with one another and can be represented as the two sides of a right triangle.
 

Thread Starter

EYT1

Joined Apr 7, 2020
84
Correct.

Specifically, 5 amps is the amplitude (the absolute value, or magnitude) of the resulting current when currents A and B are added. The Pythagorean Theorem works because the currents A and B are orthogonal-- that is, they're 90 degrees out of phase with one another and can be represented as the two sides of a right triangle.
is this the solution? is it over?
 

Thread Starter

EYT1

Joined Apr 7, 2020
84
Yep. Sure looks like the solution, to me!
Thanks. I have one more question Can you help with the solution?

One motor draws 20 Ampere lamp and 15 Ampere current. The current drawn by the lamp is in phase with the voltage; The current drawn by the motor is 60 degrees ahead of the voltage. What is the total current value drawn by the motor and lamps from the network by considering the voltage as zero phase? (cos60 = 0,5)
 

BobaMosfet

Joined Jul 1, 2009
1,124
Thanks. I have one more question Can you help with the solution?

One motor draws 20 Ampere lamp and 15 Ampere current. The current drawn by the lamp is in phase with the voltage; The current drawn by the motor is 60 degrees ahead of the voltage. What is the total current value drawn by the motor and lamps from the network by considering the voltage as zero phase? (cos60 = 0,5)
This is the hard part for you.... understanding. Don't think about formulas yet, try to understand what it is you're trying to figure out. Or what it is you're starting with. The reason it's difficult for you is because the term 'phase' is foreign to your mind.

Phase is just a fancy word that describes a point on a circle. Then entire concept of sinusoid in electronics is based on the concept that in any single cycle, you are describing every one of 360 degrees on a circle. It's not what actually happens, it's a _way to think about it_. The problem with most education is they explain things as if it's how things work, when it isn't. It's how to think about it, or convert it into a form uniform to all parts of an equation so the answer is consistent.

A sine-wave in electricity simply goes up and goes down. That's it. No circle, no degrees, nothing like that. However, in order to think about it and calculate with it, we have to convert what we know into something we can do math with.... and that's why we think in terms of phases, and sine, and vectors.

Now, up at the top of the webpage you're on, there is a wonderful section that will help you figure out what you're trying to understand:

1591395516648.png

Google is also an amazing source on vectors and _phasors_ to solve the problem you're trying to solve.
 
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