Electricity And Circuits - Class 6 Physics - Extra Questions

The Earth maintains a negative electrical potential on its surface. When we are in direct contact with the ground (walking, sitting, or laying down on the earth's surface) the earth's electrons are conducted to your body, bringing it to the same electrical potential as the earth. Living in direct contact with the earth grounds our body, inducing favorable physiological and electro-physiological changes that promote optimum health. Our body contains different fluids which contains various ions. The cells in our body also contain many ions. Therefore, our body is a good conductor of electricity.
When we are bare-footed, our body is directly in contact with the earth. When we touch wires carrying electricity, we may come in contact with a live wire. The current passes through our body to the earth & we get a shock. Hence, we should wear shoes with rubber soles (insulator) and the given statement is true.

A cell is used to operate small devices such as calculator and TV remote.Cells are supposed to supply electricity for small power devices. 

An electric circuit is a closed path in which electrons move to produce electric currents. 

Tungsten is used as filament in electric bulbs because tungsten has a high melting point and is able to withstand heat and corrosion. 

A cell is represented symbolically using two lines - one is longer that represents the positive terminal and the other is shorter that represents the negative terminal.

In a dry cell chemical energy is converted in to electrical energy.

An electric cell consists of cylindrical pot which is covered by a thick paper sheet .It consists of two terminals .One is called positive terminal ,which is the metal cap on top,and the metal disc at bottom is the negative terminal of the electric cell. The production of electric current takes place due to the chemical reactions inside the cell. The chemicals are present between the outermost covering of the cell and carbon rod.

Examples of poor solid conductors :
1) Plastic
2) Rubber 
Examples of poor liquid conductors :
1) Distilled water
2) Coconut Oil

Household Appliances

Yes, the electric circuit is closed so the bulb will glow.

CONDUCTOR : Copper

Silver metal is considered to be the best conductor of electricity.

Copper and aluminium are good conductors. So they have very low resistivities. That is why they are used in electricity transmission.

Heating effect of current is used in the working of electric fuse.

The cell will be used up rapidly in circuit A as it leads to the loss of total emf of the cell.

If the filament of a bulb is broken it is said to be a fused bulb that is that the bulb will not glow as the filament is the main glowing part of a bulb. Since, the filament is broken, the circuit is incomplete, and thus, bulb will not glow. 

Aluminium is a metal and a good conductor of electricity. So yes, the aluminium foils will act as connecting wires of connecting one strip with positive terminal of the bulb and the other with negative terminal. 

He will be successful in lighting the bulb with the given arrangement. He can connect one terminal of the bulb directly to the negative terminal of the electric cell. So he will not need any other wire for our electric circuit. The above figure explains the required arrangement

Closed circuit	Open circuit
A circuit is closed when each part of it is made of a conductor (allowing current to pass through it) and on plugging in the key or if it is complete, current flows in the circuit.	An open circuit does not allow current to flow through it, which could occur if: any of its component is not made of a conductor or the key is not plugged in or the circuit is broken.

a) Switches 2 and 3
b) The lamps are connected in series.

$$\textbf{Explanation:}$$

$$\bullet$$The closed-loop or path of electrical components in which electrons are able to flow. This path consists of electrical components source, like a battery, resistance, wire, bulb, etc.

$$\bullet$$Electric circuits are useful in many ways like all of our electrical appliances run by a particular type of circuit.

An electric circuit is a continuous conducting path for electric current consisting of a source of current and other electrical components.

The conductors of electricity are as follows:
$$\cdot$$ Copper wire: It contains free electrons for the conduction of electricity
$$\cdot$$ Acidulated water: It contains ions for the conduction of electricity
$$\cdot$$ Human body: Our body has minerals for the conduction of electricity
$$\cdot$$ Mercury: It is metal found in liquid form, it contains free electrons for the conduction of electricity

The circuit diagram for a bulb operated with a dry cell is as shown in figure.

i) Open electric circuits 
ii) Closed electric circuits 

i) Open electric circuits: The circuit in which electrical contact at any point is broken is called Open circuits 
ii) Closed electric circuits: The circuit in which electrical current flows from one terminal of a cell or battery to the other is called closed circuits. 

A material having low resistivity is a good conductor. Since, resistivity of sample A is the least among all other samples, so sample A is a good conductor. A material having high value of resistivity is an insulator. Therefore, sample C is an insulator.

(i) Current always flows from positive terminal of a battery to negative battery through the whole circuit. In case of Q to P, current will flow from positive terminal Q to negative terminal P. In case of P to Q, current will flow from negative terminal P to positive terminal Q. 
(ii) Current is flowing in both the cases so the bulb will glow in both the cases. 
(iii) The amount of current and voltage the circuit decides whether the bulb will glow brighter or duller. It is not affected by direction of current flow. 

In set A, the bulbs are connected in series. Thus, when the fuse of one bulb blows off, the circuit gets broken and current does not flow through the other bulbs also.
In set B, all the bulbs are connected in parallel. Thus, each bulb gets connected to its voltage rating ($$=220\ V$$) and even when the fuse of one bulb blows off, others remain unaffected and continue to glow.

For example if we cut the wire in a circuit, the circuit or the path for current becomes incomplete. So it is said to be open. No current flows through any part of the circuit when it is open because current only flows in closed paths.

Yes, the bulb will glow in both cases as the circuit is complete in both cases.