Effects of Electric Current:- There are three main phenomena that an electric current can produce. They are:
(1) Heating effect – When an electric potential is applied to a wire the drift of electrons is opposed by the resistance of the wire, so heat is produced. The production of electrical heat can well be compared with the production of mechanical heat with motion against frictional resistance.
(2) Magnetic effect – Oersted in the year 1819, observed that a magnetic needle placed under a current-carrying conductor is deflected, i.e. there is some relation between the current and magnetism. The conductor carrying the current does not itself become a magnet but produces a magnetic field in the space surrounding it. It is this field which acts upon the magnetic needle or soft iron pieces.
(3) Chemical effect – It has been observed that when an electric current is passed in a conducting liquid called the electrolyte, it is decomposed and the process is called as electrolysis. The electrolyte consists of solutions of acids, bases and salts such as sulphuric acid, caustic potash and copper sulphate, etc., in water. The electric current in it is conveyed by ions of both signs. All metals and hydrogen are deposited at the anode. All the above effects can be observed in Fig. 1 which consists of a heater, a cell and an electromagnet in series.
An ammeter has been used to measure current and a rheostat is inserted to vary the current. Keeping the resistance of the rheostat full in the circuit, press the key. The magnetic effect will be observed by the magnetic needle which will be deflected into the plane of paper and the armature ‘A’ will be attracted by the electromagnet. It will also be observed that the heater element becomes red hot, i.e. when the current passes through it the electrical energy is converted into heat and light energy and so it shows the heating effect of current. It will also be observed that some bubbles appear at the plate Q. These bubbles are of hydrogen which is liberated there. After a few minutes if the plate P is taken out, it will have a brown chocolate color of lead oxide. So it follows that the electrical energy has been converted into chemical energy in changing the lead to lead oxide. The deflected needle of the ammeter shows the presence of the current in the circuit. Now if the resistance of the rheostat is decreased it will be observed that all the effects increase together.