ELECTRIC CURRENT & ITS EFFECTS

**ELECTRIC CURRENT AND ITS EFFECTS**

1.      Define electric circuit?

Ans: Connection of electronic components, through which an electric current can flow.

2.      Draw symbols of fuse, variable resistor and galvanometer.

Ans: 

3.      How to connect voltmeter and ammeter in a circuit?

Ans: We need to connect voltmeter in parallel, across the electronic components and ammeter in series with electronic components.

4.      Draw a simple circuit with a bulb, switch and a resistor and also draw appropriate positions of voltmeter and ammeter to measure voltage across resistor and bulb.

5.      Payal connected a simple circuit with a cell, switch, resistor and bulb in series. She measured current through a bulb, resistor and she found that the ammeter reads same value. Why?

Ans: In series connection the current at every point is same, so if we connect ammeter at any point it will read the same value.

6.      Write the advantages of parallel connection over series connection.

Ans: In parallel connection, all the components get same amount of voltage, but in series connection, the voltage is divided according to their resistance value. If one component goes bad other will work, but in series connection if one goes bad others also will not work.

7.      Define open and closed circuit?

Ans: If the path of the electricity/current is broken or if the switch is open in any electric circuit, then the circuit is said to be an open circuit. If the path of electric current is not broken then the circuit is said to be closed circuit. Current will never flow in open circuit.

8.      What do you mean by a short circuit?

Ans:  If line(phase) or positive terminal and neutral wire get connected with each other, then a high current will flow through the wire this is  called short circuit.

9.      Write the applications of heating effect of electric current.

Ans: The heating effect of current is used in a large number of industrial and domestic appliances, such as

·         Immersion heaters

·         Hot plates, irons

·         Geysers

·         Electric kettles

·         Hair dryers.

10.  Write the applications of magnetic effect of electric current.

Ans:  Magnetic effect of electric current is used in Electromagnets

·         To remove iron splinters from our eyes/ body.

·         It is used in the cranes to lift heavy objects.

·         In loudspeakers

·         In telephone receiver and in the microphone.

·         In relays- to switch ON high power electric motors.

·         In electric motors, D.C. motors, electric fans they use electromagnet to convert electrical energy into mechanical energy.

11.  How wires get heated, when current flow through wires?

Ans: Every wire will have small resistance, when high current flows through these wires because this resistance heat is generated.

12.   Write the reasons for excessive current

Ans: A short circuit is the main reason for excessive current. Short circuit arises due to defect in the house wiring or insulation on wires, connection of many devices to a single socket may leads to overloading.

13.   The wires used for making electric circuit do not normally become hot. Why?

Ans: The wires which are used in circuit are good conductors, they have very low resistance (almost zero). So they will not get heated if current flow through them.

14.  In the below given diagram how can we control the brightness of the bulb? If we change the resistance from 0 to 100 Ω (ohms) write the voltmeter reading with resistance change.

Ans: In the above circuit variable resistor is connected in series with the bulb, so if we change the resistance of variable resistor the voltage across the bulb is also changes from 0-9V. So the brightness of the bulb changes with the resistance. The voltmeter across the bulb reads 0-9V.

15.   In the below given diagram

A.    Voltmeter 1 reading=?

B.     Voltmeter 2 reading=?

C.    Write the reading of both ammeters. What do you understood from these readings of ammeter?

Ans:  A. Voltmeter 1 reads 9V.

B. Voltmeter 2 reads 9V. (Because in parallel connection voltage across each component is same)

C. Both the ammeters reads same value i.e., 200mA. Because the in closed circuit is the current is same at any point. 

ALL THE BEST