BBC - GCSE Bitesize: Resistance and Ohm's Law
Moving the amp from your test bench to the floor takes work, in this case negative work because the . The relationship between voltage, current, and power is. The equation below shows the relationship between resistance, voltage, current: The current flowing through a resistor at a constant temperature is directly. Definitions of the Ohm Ampere and Volt. In doing so he devised his law which shows the inter-relationship between the three basic electrical Ohm´s Law states that: "In metallic conductors at a constant temperature and in a zero magnetic.
These are just some of the definitions of work that have no meaning to a physicist like Georg Simon Ohm. To him work is required to move an object against a force that opposes its motion. So lifting your Hiwatt DR from the floor to your work bench requires work, because you are moving the amp upwards against the force of gravity that opposes it. On the other hand, carrying a Twin Reverb around the block is no work at all, because the amp is moving horizontally - gravity does not oppose the movement in that direction.
Resistance and Ohm's Law
So when the road crew complains just refer back to this tutorial and explain to them why there is no work involved. Moving the amp from your test bench to the floor takes work, in this case negative work because the direction of motion is helped along by the force of gravity. If all this sounds strange already, just add this concept to the mix: It takes a specific amount of work to lift your DR to the bench. It doesn't matter whether you jerk it upwards in a fraction of a second or take 20 minutes to lift it over the same path.
Temperature change and resistance
It is the same amount of work. When the opposing force is measured in newtons and when the distance traveled against the opposing force is measured in meters, then the work, measured in joules, is the force times the distance: It turns out that a kilogram is a unit of mass.Volts, Amps, and Watts Explained
The force that we think of when we try to lift that parallel push-pull boat anchor is the mass times the acceleration of gravity, which happens to be 9. When we multiply the number of kilograms by 9. Problem The output transformer for your watt push-pull amp weighs 6. When holding it in your hands, what is the force of gravity pulling it downward?
The force of gravity in newtons is then 3kg 9. The top of your bench is 1.
Strip coating from the ends to allow electrical contact via crocodile clips. Procedure a Set up a simple series circuit with long leads to the loosely wound coil of copper wire. Switch the circuit off, as soon as possible.
Work, Voltage, and Power
Switch the circuit on again. Take readings of the ammeter and voltmeter several times during the next half-minute or so. During this time the coil heats up and the current changes quite rapidly.
The water should be kept very well stirred. Take care to avoid short-circuiting the coil by using a wooden lolly stick or spatula as the stirrer.
This is not a straight line showing constant resistance, but rather a curve showing that the resistance of the wire increases with temperature. Pure metals do obey Ohm's law when their temperature remains constant. 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.