Electricity: Coulomb's Law

Coulomb's Law

The ancient Greeks found that a piece of amber, when rubbed became electrified and attracted pieces of straw or feathers. In 1785, Charles Coulomb describes experiments that confirmed the inverse-square force law of electricity.

Coulomb's law is the fundamental law of force. Coulomb's law discusses the force between two stationary charged particles. STATIONARY, please bear in your mind!
(we'll learn a different concept for the MOVING charges)
Knowing that, there are two type of charges: that are positive and negative charges. The Coulomb force can be attractive and/or repulsive where it depends on the types of charges interacted.

Like charges repel one another
Opposite charges attract one another

Let's understand this example of experiment, an inflated balloon is rubbed with wool . The balloon will then stick to the wall of a room, often for hours (on a dry day). Rubbing the balloon with the wool is equivalent to taking off the negative charge from the wool onto the balloon. The balloon is now negatively charged and it is able to attract positively charged wall. The attraction is called Coulomb force.

Image result for balloon wool paper electrostatics

Application of electrostatics:

Can you imagine the phenomena of flash during thunderstorm, minor electric shock at the supermarket trolleys?? Have you ever seen/experienced them?

During thunderstorm, there is a higher (than normal) electric field created between the charged cloud and the negatively charged earth's surface.

Thank you,

Mdm Ummi Atiah KMPk

~ May it Benefits You ➽💕

Comments

Electric Potential

Electric Potential, V If Ali wants to move his charge towards the charged sphere on the left, he has to push against the repulsive force between the two spheres (because both are positively charged) Ali is actually doing work (when he push) , Remember W= f.s ! At the same time, Ali's charge gains electric potential energy . If Ali let go his charge, it will move away from the sphere, it looses electric potential energy. The electric potential at a point is telling us the potential energy of each coulomb of charge . When you move a charge in an electric field its potential energy changes. This is analogous to moving a mass in a gravitational field. Electric potential is a scalar quantity. Thank you, Mdm Ummi Atiah KMPk ~ May it Benefits You ➽💕

Root Mean Square Current (I rms)

Root Mean Square Current As mentioned in the previous post , the value of AC is always changing. Then, how do we measure its value??? We could not use the maximum value of the current Io, because it only occurs at a moment. The average current is ZERO . Hence, one effective value that we could use the root mean square value. Irms . The formula for Irms is given by: where Io is maximum current. Irms is the value that is equivalent to a steady direct current . We can investigate this by comparing 2 circuits containing lamp each. circuit 1 uses battery as the source, while circuit 2 uses a.c. supply. AC supply is adjusted so that both lamps are equally bright. At this point, DC and AC supplies are transferring energy to the lamps at the same rate (Power). By equating the Power of both circuits, we can deduce the equation of Irms as above. Therefore, the d.c. voltage equals the r.m.s. value of the a.c. voltage. From the the graph below and th...

Magnetic Field

Magnetic Field, B To define Magnetic field, we start with the word field. Field means a region or space. The magnetic field is defined as a region where the magnetic force can be felt. In other words, a force (repel/attract) can be felt in the region. Bar Magnet We will find that 2 North(N) poles will repel if we bring the poles of two bar magnets together. Same goes to that of 2 South(S) poles. However North and South pole attracts. The strength and direction of the field are represented by lines. Knowing that, the direction of magnetic field is from North to South. Magnetic field is able to be detected by 1) Compass (have been used over 2000 years 2) Hall Probe Applications: Swipe cards, Video tapes & Computer discs -use magnetism to store information. History: In 1819, Hans Christian Oersted noticed that a compass needle was deflected by an electric current in a nearby wire. Remember!! the compass is used to detect any existance of magnetic field. By th...

Think Like A Proton, Always Positive :)

Search This Blog