- What is Electricity?
- Current, Voltage and Resistance
- How to measure Current, Voltage and Resistance
- How Electricity works?
Electric current is the ability to do work. Electric current can be converted to heat, power and magnetism, to name a few.
Electric current is classified by its functions and three primary types are:
- Heat and power
Heat and power is used to make heat and power.
For example, current-carrying nichrom wire that nichrom wire has a high resistance and creates heat. This is applied to be component of electric ovens, toasters, electric irons and light bulbs, etc.
Experiment is made by measuring heat quantity of water by calorimeter. Increase voltage across wire by the variac and connect ammeter and voltmeter to measure current and voltage.
Set the variac scale to adjust voltage and current value of nichrom wire and current is passed through periodically and measure heat quantity from nichrom wire. There are any indications of voltage and current. If voltage, current and time increase, heat quantity will also increase. They are expressed by the relation as below.
This is called Joule’s law. Heat quantity depends on voltage time current and interval of time. From Ohm’s law, V (Voltage) = I (Current) x R (Resistance) therefore
Heat quantity depends on current squared times resistance and interval of time.
When current is passed through nichrom wire in water, current is converted to heat and temperature rises. Work is done by heat generated in an electrical circuit, which is called Electric power.
Electric power is measured in Watts-hour (Wh) and heat quantity is measured in calories (Cal).
Work is done by heat generated in an electrical circuit is written in power, which it means that the rate work is done in a circuit when 1 Amp flows with 1 Volt applied and its unit of measurement is Watt.
For example, when current is passed through sodium chloride (NaCl) solution, a chemical reaction called electrolysis occurs. This is applied to produce electrolysis, galvanizing and battery, etc.
Experiment is made by soaking two platinum (Pt) plates in molten salt. Connect batteries to two platinum plates, current is passed through molten salt and produces chlorine bubbles around positive plate (+) and hydrogen bubbles around negative plate (-) since sodium chloride composes of sodium (Na) and chloride (Cl). When sodium chloride melts in water, the elements are separated. Sodium has positive charges (+), while chlorine has negative charges (-) and these charges are called ions. The molten salt has both positive charges, called anodes, and negative charges called cathodes. The state of separated elements is called ionization. If salt is melted by water, solution is available ions, called electrolyte solution. And if current is passed through electrolyte solution, a chemical reaction known as electrolysis occurs.
The example of this electric work is a current-carrying wire, magnetic lines of flux occur. This is applied to produce electric motors, electric transformers and tape recorders, etc.
Understanding meaning of magnetism:
What is magnetism?
The compound formula of magnet is Fe3O4. All magnets have two characteristics. First, they attract and hold iron. Secondary, if free to move like the compass needle, they will assume a north-south position. Any materials have these characteristics, they are called magnet.
The characteristics of magnet are
- Every magnet has two poles, one north pole and one south pole.
- Opposite poles attract each other, while like poles repel each other.
Electricity and magnetic field
When magnetic needle is placed near electric wire, which current is passed through, magnetic needle turns on the direction of current flow (see figure 1 and 2). Therefore, electric current flow also produces an associated magnetic force or it is said that electricity is able to produce magnetic field.
When magnetic needle is placed in wire coil with one loop (see figure) and current is passed through wire coil, magnetic needle turns on the direction as shown in above figure. And the directions of magnetic lines of flux are shown by the arrows.
When magnetic needle is placed in wire coil with many loops as shown in right figure, then current is passed through coil. The direction of magnetic lines of flux parallels wire coil. The characteristics of magnetic lines of flux like the characteristics of magnet, but no magnetic pole.
When a current-carrying wire coil is placed near iron bar, the iron bar move slightly (see figure 1). If core is placed in a wire coil, the iron bar is attracted strongly (see figure 2). Because core is a soft iron, which conducts magnetic lines of force, when current is passed through wire coil around core, the core becomes magnetized with high power that is called electromagnets. This function is widely applied for using in industries.