# Relationship between current flow and resistance

### Current and Resistance

Using the flow analogy, electrical resistance is similar to friction. The connection between voltage and resistance can be more complicated in. Ampere is the unit of electrical current that will flow through one ohm the relationship between current, voltage, and resistance in an electric. The first, and perhaps most important, relationship between current, voltage, and and also the amount of resistance in the circuit to oppose electron flow.

When we speak of a certain amount of voltage being present in a circuit, we are referring to the measurement of how much potential energy exists to move electrons from one particular point in that circuit to another particular point.

Free electrons tend to move through conductors with some degree of friction, or opposition to motion.

This opposition to motion is more properly called resistance. The amount of current in a circuit depends on the amount of voltage available to motivate the electrons, and also the amount of resistance in the circuit to oppose electron flow.

## 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. The resistivity for a specific conductor can be found in a table of properties of materials. Resistance to current in a conductor arises because the flow of moving charges is impeded by the material of the wire.

The relationship between resistance and resistivity is Note: A resistor is a specific electronic component whose only function is to resist current. A resistance is generated by anything impeding current, for example, a light bulb or heating element. Electrical power and energy Figure 1 shows a simple circuit of a battery with wires connecting it to a bulb. The filament in the bulb is a resistance shown in the circuit as R beside the symbol for a resistance.

### Current and resistance

Assume that the resistance in the connecting wires is negligible so that the light bulb is effectively the only resistance in the circuit. A constant potential difference is supplied by the battery—say, for example, 6 volts. When the current passes through the light bulb, charges move from a higher potential to a lower, with a difference of 6 volts.

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.

## Current and Resistance

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.

**Electronics Tutorial #4 - Ohm's Law Pt 1 - Relationship between Current, Voltage and Resistance**

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.

### BBC Bitesize - GCSE Physics (Single Science) - Current, voltage and resistance - Revision 4

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: