According to the flow of charged particle in a circuit, there are two types of current.
Fuse is the special wire that melts when a certain amount of electricity flows through it. It happens due to heating effect (link to the heating effect) caused by electricity and we are going to talk about it later on. Fuses are made according to the maximum amount of current flowing into the circuit. If a circuit needs small amperage of current then we can use fuse with low amperage (in household normally 5 to 15A of fuse is used) and if the circuit needs high amount of current then high amperage of fuse is used (in small scale industries up to 30A of fuse is used and in heavy industries fuse use varies greatly). Fuse is made from a special alloy of tin and lead and the amount of lead and tin determines the capacity of the fuse. The small wire is enclosed in a glass case and sealed with small iron plates. But if we are using a fuse box then, the setting is different.
Selection of fuse:
To know what capacity of a fuse to use we have to find out how much of current is needed in the circuit. For that, we have to know the potential difference (V) of the circuit and total power drawn (P) by the appliances in that circuit. Using the formula, I = PV.We know the total current flowing in the circuit. Now if we use a fuse that has less amperage than the current flowing in the circuit the fuse cannot handle the flow of charged particles and breaks. So, we have to use the slightly higher capacity of fuse than that of current in our circuit.
When we see a wire we actually see copper wire enclosed in a casing of different colors. Those casings are there to insulate the wire and we do not get a shock while touching it. The colors of the wire differ according to their type and country it is found. Normally in Nepal live wire has a red casing to it, neutral has black and earthing has a yellow color. But some might use brown colored wire for live wires, blue for neutral and green for earthing. The coloration is done because it is easier to know which wire is live or neutral or earthing.
In household wiring, all of the electric bulbs with separate circuit are connected in parallel and each of the bulbs is controlled by a separate switch. The advantage of parallel circuit is that by using different switches, we can turn on and off the bulbs according to requirement.
The electrical appliances are connected in parallel because the parallel connection of the appliances has the following advantages: -
The domestic wiring is not done in series circuit because: -
The electric wire which supplies electric power to the electrical appliances is called phase or live wire. In household wiring, it is red in colour.
A fuse is a safety device which is made up of tin and lead alloy and gets connected to the circuit in such a way that it controls the maximum limit of current passing through the circuit by melting itself.
A fuse wire should have the following characteristics: -
A copper wire cannot be used as a fuse because it has high melting point and low resistance. Due to this reason, it does not easily melt and the circuit is not broken.
The capacity of the fuse is measured in terms of the unit Ampere. To find the capacity of the fuse, it is necessary to know potential difference and amount of current that flows. Then the multiplication of two gives the minimum value of fuse. For the fuse, it is required to use slightly high capacity fuse than the calculated value.
Fuse should always be connected with a live line. When the fuse goes off, current is cut off and there is no chance of electric shock.
Fuse should be always connected to the live or phase wire so that if the fuse is broken due to the over current strength there won't be electrical accident as well as there won't flow the current to the equipment.
When two wires are connected directly in an electric circuit, electric spark appears and the circuit is shorted which is called short circuit. The spark is due to the large flow of current.
The arrangement of the electric circuit to make the flow of charges to the earth is called earthing.
The earthing prevents the damage of the property, life and also prevents the electric leakage. It also saves the damage from the lighting.
In electrical appliances and electronic devices by short circuit or any means, flow of current may take place. Due to over flow of current in the devices, they may damaged. To prevent such damages, one of the way is to make the charge or current flow to the earth. For such purpose, the appliance is connected to the earth and is called earthing.
The two advantages of making these covers colourful are as follows: -
The polarity of the current does not change in ______.
both AC and DC
The polarity of the current changes according to its frequency in ______.
both AC and DC
The polarity of electricity provided in Nepal changes _______.
50 times second
60 times second
61 times second
51 times second
The special wire that melts when certain amount of electricity flows through it is ______.