# Relationship between power current and potential difference across a capacitor

### BBC Bitesize - Higher Physics - Current, potential difference, power and resistance - Revision 1

Calculate the voltage drop of a current across a resistor using Ohm's law. consider the loss of electrical power, called a voltage drop, in each resistor in [ link]. the formula V=IR is used to find the potential difference, in volts, is the drop in voltage that occurs across a resistor as current flows through it. For Higher physics, revise problem solving applied to resistor nee potential dividers and other This relationship expresses the law of conservation of energy.

Once the water or the roller coaster cars reach high gravitational potential, they naturally move downward back to the low potential location. For a water ride or a roller coaster ride, the task of lifting the water or coaster cars to high potential requires energy. The energy is supplied by a motor-driven water pump or a motor-driven chain. In a battery-powered electric circuit, the cells serve the role of the charge pump to supply energy to the charge to lift it from the low potential position through the cell to the high potential position.

It is often convenient to speak of an electric circuit such as the simple circuit discussed here as having two parts - an internal circuit and an external circuit. The internal circuit is the part of the circuit where energy is being supplied to the charge. For the simple battery-powered circuit that we have been referring to, the portion of the circuit containing the electrochemical cells is the internal circuit. The external circuit is the part of the circuit where charge is moving outside the cells through the wires on its path from the high potential terminal to the low potential terminal.

The movement of charge through the internal circuit requires energy since it is an uphill movement in a direction that is against the electric field. The movement of charge through the external circuit is natural since it is a movement in the direction of the electric field. When at the positive terminal of an electrochemical cell, a positive test charge is at a high electric pressure in the same manner that water at a water park is at a high water pressure after being pumped to the top of a water slide.

Being under high electric pressure, a positive test charge spontaneously and naturally moves through the external circuit to the low pressure, low potential location.

### Power, Current & Potential Difference Across a Resistor | fabula-fantasia.info

As a positive test charge moves through the external circuit, it encounters a variety of types of circuit elements. Each circuit element serves as an energy-transforming device. Light bulbs, motors, and heating elements such as in toasters and hair dryers are examples of energy-transforming devices.

In each of these devices, the electrical potential energy of the charge is transformed into other useful and non-useful forms. For instance, in a light bulb, the electric potential energy of the charge is transformed into light energy a useful form and thermal energy a non-useful form.

• Voltage, Current, and Resistance

The moving charge is doing work upon the light bulb to produce two different forms of energy. By doing so, the moving charge is losing its electric potential energy. Upon leaving the circuit element, the charge is less energized.

The location just prior to entering the light bulb or any circuit element is a high electric potential location; and the location just after leaving the light bulb or any circuit element is a low electric potential location.

Referring to the diagram above, locations A and B are high potential locations and locations C and D are low potential locations.

The loss in electric potential while passing through a circuit element is often referred to as a voltage drop. By the time that the positive test charge has returned to the negative terminal, it is at 0 volts and is ready to be re-energized and pumped back up to the high voltage, positive terminal.

Electric Potential Diagrams An electric potential diagram is a convenient tool for representing the electric potential differences between various locations in an electric circuit.

Two simple circuits and their corresponding electric potential diagrams are shown below. In Circuit A, there is a 1. In Circuit B, there is a 6-volt battery four 1. In each case, the negative terminal of the battery is the 0 volt location.

The positive terminal of the battery has an electric potential that is equal to the voltage rating of the battery. The battery energizes the charge to pump it from the low voltage terminal to the high voltage terminal. By so doing the battery establishes an electric potential difference across the two ends of the external circuit. Being under electric pressure, the charge will now move through the external circuit.

## Current, potential difference, power and resistance

As its electric potential energy is transformed into light energy and heat energy at the light bulb locations, the charge decreases its electric potential. Resistors do more than just influence the amount of current in the circuit, though. Because it's difficult for the electrons to get through the resistor, they give up some energy as they pass through.

That energy doesn't disappear: Light bulbs are one type of resistor that transform electrical energy into both thermal energy and light energy.

Light bulbs are resistors that transform electrical energy into light Ohm's Law If you wanted to experimentally determine the relationship between current, voltage, and resistance, what could you do? A good way to determine this relationship would be to measure the current in a circuit composed of a voltage source, like a battery, and a resistor. You could change the amount of voltage, perhaps by varying the number of batteries used, and see how the current changed in response.

When measuring quantities like voltage, resistance, and current, it's really important to make sure that you are using the correct units. Typically, current is measured in units of Amperes Avoltage is measured in Volts Vand resistance is measured in Ohms. Once you measured the current in A and voltage in Va graph could help you to understand the data. If you plotted the voltage on the y-axis and the current on the x-axis, you would get a graph similar to the one shown below: This graph gives you some pretty important information about what is going on in the circuit.

First, did you notice that the graph formed a straight line? This means that there is a direct relationship between current and voltage for this resistor. We call this relationship Ohm's law, which says that the current through a resistor is directly proportional to the voltage and inversely proportional to the resistance of the resistor.

However, as the resistance goes up, the current goes down. Think back to the cars trying to get past the accident on the highway.