Think Like A Proton, Always Positive :)

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...

Alternating Current (AC) DC versus AC  Remember in Chapter 18, we learned direct current  (DC). Direct current means a current that is flowing in only one direction, that is from positive terminal to the negative terminal of the battery in the circuit. Battery is one of the examples of DC source, while AC generator is the source of AC. The meaning of the word 'alternate' is something occurs by turns; first one and then the other. Knowing that alternating current (AC) means the direction of a current always changing its turns. The proper definition of AC  is a current that repeatedly reverses its direction . Alternating current is not only changing its direction, but it also changes its value. It does not have any similar values. This can be seen clearly from the GRAPH 2 below, in which you can also compare it with that of DC. GRAPH: AC VERSUS DC When it comes to calculation, we don't have any problem in writing down the value of DC because it is alway...

Electromagnetic Induction In the previous entry, we have seen that current, I can produce magnetic field, B. In this entry, we are going to look the other way round where B can also produces I. This concept that we will discuss here is induction. In 1831, Michael Faraday discovered that Power stations generate electricity by using electromagnetic induction. Diagram 1 Diagram 1 will helps us to explain the meaning of electromagnetic induction.The wire is connected to a galvanometer. Do you still remember the function of galvanometer? Please have a think!! What happens if we move the wire up and down in the region of the magnetic field? The galvanometer needle will flick to one side and another. It shows here that current is induced. But, if the wire does not moved, there will be no induced current. If there is an induced current, meaning there is also an induced voltage (or known as induced emf). Hence, we can conclude here that when a wire(conductor) is moving in a m...

Electromagnetism The word electromagnetism is actually combining the words electric current , I (electro) and magnetic field, B (magnetism). Electromagnetism means magnetic field can be produced by the current. In matriculation syllabus, there are 3 cases of wire that carries current producing magnetic field . These wires are having different forms that are : 1) straight 2) Coil/loop 3) Solenoid. Equations: The equations show that they  are not the same. For the moment I'm not going to derive the equations of the magnetic field, but I'll just talk a little bit about it in order to give you some useful tips.                                                                         I believe many of you might get confused   (tertukar) at first with the equations of magnetic f...

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...

Potentiometer Potentiometer is a device that is equivalent to a circuit . It actually applies the same concept as that of potential divider. Do you still remember the principle of potential divider? If not, please refer here . Physically, this is how a potentiometer looks like ( one example): Normally we use the variable resistor as the potentiometer to control the voltage. Before I explain any further, please refer Diagram 1 and Diagram 2 below: Diagram 1: Potential Divider                                   Diagram 2: Potentiometer If we could realize, both Diagram 1 & Diagram 2 are quite similar. In Diagram 2, we have that black thick wire of from A to B. As we know, the resistance of any wire is always directly proportional to wire which means that , the longer the wire the higher the resistance.  l directly proportional with R In the middle of wire AB,...

Potential Divider Potential divider is also known as voltage divider. Its purpose is to be used to obtain any desired( wanted/preferred) smaller portion of voltage from a single source, V T. i.e. sometimes we want to use only part of the voltage provided by a battery and in order to get this, we use a potential divider circuit. Potential divider consists of 2 resistors that are connected to a voltage source. Diagram 1: Potential Divider  The basic principle of a potential divider circuit is that the resistors in the circuit act as the divider . The value of the resistance of each resistor  will influence the value of the voltage. Example/Application in real life: Th e rotary type of potentiometer. (1) We control the volume of the radio by twisting its knob. (2) We control the fan speed by twisting the 1-2-3-4-5 knob. Is not it?? So, what we are doing (example 1 & 2) here is we actually controlling the resistance, resulting in the voltage port...