Resistance equation with voltage and current relationship

Electrical/Electronic - Series Circuits Electric power basic formulas calculator voltage current mathematical equation formula for Relationship of the physical and electrical quantities (parameters). A parallel circuit has two or more paths for current to flow through. Voltage is the same across each component of the parallel circuit. The sum of the You can find total resistance in a Parallel circuit with the following formula: 1/Rt = 1/R1 +. Similarly, increasing the resistance of the circuit will lower the current flow if the voltage is not changed. The formula can be reorganized so that the relationship.

The V is the battery voltage, so if R can be determined then the current can be calculated. The first step, then, is to find the resistance of the wire: L is the length, 1. The resistivity can be found from the table on page in the textbook.

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The area is the cross-sectional area of the wire. This can be calculated using: The resistance of the wire is then: The current can now be found from Ohm's Law: It has units of Watts. Batteries and power supplies supply power to a circuit, and this power is used up by motors as well as by anything that has resistance. The power dissipated in a resistor goes into heating the resistor; this is know as Joule heating. In many cases, Joule heating is wasted energy. In some cases, however, Joule heating is exploited as a source of heat, such as in a toaster or an electric heater. The electric company bills not for power but for energy, using units of kilowatt-hours. It does add up, though. The following equation gives the total cost of operating something electrical: Try this at home - figure out the monthly cost of using a particular appliance you use every day.

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.

Current and resistance

The cost for power that comes from a wall socket is relatively cheap. 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.

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

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. 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: In this algebraic expression, voltage E is equal to current I multiplied by resistance R.

Using algebra techniques, we can manipulate this equation into two variations, solving for I and for R, respectively: In the above circuit, there is only one source of voltage the battery, on the left and only one source of resistance to current the lamp, on the right. In this first example, we will calculate the amount of current I in a circuit, given values of voltage E and resistance R: What is the amount of current I in this circuit?

Voltage, Current, Resistance & Power

In this second example, we will calculate the amount of resistance R in a circuit, given values of voltage E and current I: What is the amount of resistance R offered by the lamp?