# How is power determined using voltage and current relationship

### Ohm's Law Calculations With Power

Power is the ability to do work and is measured in Watts. The higher the voltage the more power you have with the same current (Watts (power) = Volts x Amps. They are Power (P) or (W), measured in Watts, Voltage (V) or (E), measured in Volts, Current or Amperage (I), measured in Amps (Amperes), and Resistance (R ). Theory an definitions on measuring voltage, current, power and energy. The current has a top value of 2 A and is shifted 60° in relation to the voltage. In digital meters, this average established by means of a RC-filter.

## Ohm’s Law - How Voltage, Current, and Resistance Relate

Just like voltage, resistance is a quantity relative between two points. Volt, Amp, and Ohm To be able to make meaningful statements about these quantities in circuits, we need to be able to describe their quantities in the same way that we might quantify mass, temperature, volume, length, or any other kind of physical quantity.

Here are the standard units of measurement for electrical current, voltage, and resistance: Standardized letters like these are common in the disciplines of physics and engineering, and are internationally recognized.

Each unit of measurement is named after a famous experimenter in electricity: The amp after the Frenchman Andre M. The mathematical symbol for each quantity is meaningful as well.

- Ohm's Law Calculations With Power
- Calculating Electric Power
- Electrical power

Most direct-current DC measurements, however, being stable over time, will be symbolized with capital letters. Coulomb and Electric Charge One foundational unit of electrical measurement, often taught in the beginnings of electronics courses but used infrequently afterwards, is the unit of the coulomb, which is a measure of electric charge proportional to the number of electrons in an imbalanced state. One coulomb of charge is equal to 6,,, electrons. Cast in these terms, current is the rate of electric charge motion through a conductor.

As stated before, voltage is the measure of potential energy per unit charge available to motivate electrons from one point to another. Defined in these scientific terms, 1 volt is equal to 1 joule of electric potential energy per divided by 1 coulomb of charge.

Thus, a 9 volt battery releases 9 joules of energy for every coulomb of electrons moved through a circuit. These units and symbols for electrical quantities will become very important to know as we begin to explore the relationships between them in circuits.

Ohm expressed his discovery in the form of a simple equation, describing how voltage, current, and resistance interrelate: Possibilities include hair dryers, microwaves, TV's, etc. The power rating of an appliance like a TV is usually written on the back, and if it doesn't give the power it should give the current.

Anything you plug into a wall socket runs at V, so if you know that and the current you can figure out how much power it uses. The cost for power that comes from a wall socket is relatively cheap.

### BBC Bitesize - National 5 Physics - Electrical power - Revision 1

On the other hand, the cost of battery power is much higher. Although power is cheap, it is not limitless. Electricity use continues to increase, so it is important to use energy more efficiently to offset consumption. Appliances that use energy most efficiently sometimes cost more but in the long run, when the energy savings are accounted for, they can end up being the cheaper alternative.

Direct current DC vs. If the circuit has capacitors, which store charge, the current may not be constant, but it will still flow in one direction.

The current that comes from a wall socket, on the other hand, is alternating current. With alternating current, the current continually changes direction.

This is because the voltage emf is following a sine wave oscillation. For a wall socket in North America, the voltage changes from positive to negative and back again 60 times each second.

You might think this value of V should really be - volts. That's actually a kind of average of the voltage, but the peak really is about V. This oscillating voltage produces an oscillating electric field; the electrons respond to this oscillating field and oscillate back and forth, producing an oscillating current in the circuit.

The graph above shows voltage as a function of time, but it could just as well show current as a function of time: Root mean square This average value we use for the voltage from a wall socket is known as the root mean square, or rms, average. Because the voltage varies sinusoidally, with as much positive as negative, doing a straight average would get you zero for the average voltage.

The rms value, however, is obtained in this way: To find the rms average, you square everything to get 1, 1, 9, and Finally, take the square root to get 3. The average is 2, but the rms average is 3. Doing this for a sine wave gets you an rms average that is the peak value of the sine wave divided by the square root of two. This is the same as multiplying by 0. If you need to know about the average power used, it is the rms values that go into the calculation.

Series circuits A series circuit is a circuit in which resistors are arranged in a chain, so the current has only one path to take. The current is the same through each resistor. The total resistance of the circuit is found by simply adding up the resistance values of the individual resistors: A series circuit is shown in the diagram above.

The current flows through each resistor in turn.

If the values of the three resistors are: The current through each resistor would be 0. Parallel circuits A parallel circuit is a circuit in which the resistors are arranged with their heads connected together, and their tails connected together. The current in a parallel circuit breaks up, with some flowing along each parallel branch and re-combining when the branches meet again.

The voltage across each resistor in parallel is the same. The total resistance of a set of resistors in parallel is found by adding up the reciprocals of the resistance values, and then taking the reciprocal of the total: A parallel circuit is shown in the diagram above.

In this case the current supplied by the battery splits up, and the amount going through each resistor depends on the resistance. The voltage across each resistor is 10 V, so: A parallel resistor short-cut If the resistors in parallel are identical, it can be very easy to work out the equivalent resistance. In this case the equivalent resistance of N identical resistors is the resistance of one resistor divided by N, the number of resistors. So, two ohm resistors in parallel are equivalent to one ohm resistor; five ohm resistors in parallel are equivalent to one ohm resistor, etc.