1. Write proper words from the following group in the blank and rewrite complete sentences

(magnetism, 4.5V, 3.0V, gravitational attraction, potential difference, potential, higher, lower, 0V)

Question a.Water in the waterfall flows from a higher level to a lower level because of …………….

Answer: Water in the waterfall flows from a higher level to a lower level because of gravitational attraction.

Question b.In an electric circuit, electrons flow from a point of potential to the point of ……….. potential.

Answer: In an electric circuit, electrons flow from a point of lower potential to a point of higher potential.

Question c. The difference between the electrostatic potential of the positive end and the negative end of an electric cell is the …………. of the cell.

Answer: The difference between the electrostatic potential of the positive end and the negative end of an electric cell is the potential difference of the cell.

Question(d). Three electric cells of potential difference of 1.5 V each have been connected as a battery. The potential difference of the battery will be ……………… V.

Answer: Three electric cells of potential difference of 1.5 V each have been connected as a battery. The potential difference of the battery will be 4.5 V.

Question e. An electric current flowing in a wire creates ………………… around the wire.
Answer: An electric current flowing in a wire creates magnetism around the wire.

2. A battery is to be formed by joining 3 dry cells with connecting wires. Show how you will

Question 3. In an electric circuit, a battery and a bulb have been connected and the battery consists of two cells of equal potential difference. If the bulb is not glowing, then which tests will you perform to find out the reason for the bulb not glowing?

Answer: If the filament of the lightbulb is visible, inspect it for any breaks or defects. Also, make sure that the cells are connected properly.

Question4.Electriccellshavingapotentialdifferenceof2Veachhavebeenconnectedintheformofabattery. What will be the total potential difference of the battery in both cases?

Answer:
(i) 6V
(ii) 8V.

In the first case, three cells are connected in series.
∴Total potential difference=2V+2V+2V=6V.
In the second case, four cells are connected in series.
∴Total potential difference=2V+2V+2V+2V
=8V]

When three 2 V cells are connected in series, the total potential difference is 6 V. This is because the voltage of the cells are added together in a series connection. Similarly, when four 2V cells are connected in series, the total potential difference is 8V.

Question5.Describes the construction, working, and usefulness of a dry cell, the with the help of a diagram.

Dry cell

Adrycellisatypeofelectrochemicalcellthatusesapasteofchemicalsastheelectrolyte.Thecellconsistsofazincmetalcontainer(negative electrode)and a graphite rod(positive electrode) surrounded by a paste of manganese dioxide and ammonium chloride. When the cell is connected to a circuit, the chemicals in the paste react, producing electrons at the zinc electrode and a positively charged manganese dioxide at the graphite electrode. These electrons flow through the circuit, creating an electric current.

Drycellsarecalled”dry”becausetheydonotcontainaliquidelectrolyte.Instead,theelectrolyteisapastethatisheldinplacebyaporousmaterial.Thismakesdrycellsmorestableandlesslikelytoleakthancellswithliquidelectrolytes.

Drycellsareacommontypeofbatteryusedinavarietyofdevices,includingflashlights,radios,andtoys.Theyarealsousedinsomemedicaldevices,suchashearingaidsandpacemakers.

Here are some of the advantages of dry cells:

• They are relatively in expensive.
• They are easy to use and can be held in any direction.
• They have a long shelf life.

Here are some of the disadvantages of dry cells:

• They do not produce as much current as other types of batteries.
• They can be damaged if they are dropped or shaken.
• They can leak if they are not handled properly.

6.Describetheconstructionandworkingofanelectricbellwiththehelpofadiagram.

Answer.Anelectricbellisanelectromechanicaldevicethatproducesasoundwhenanelectriccurrentispassedthroughit.Itismadeupofthefollowingparts:

• Anelectromagnet:Thisisacoilofwirethathasapieceofironinsideit.Whenanelectriccurrentispassedthroughthecoil,theironbecomesmagnetized.
• Anarmature:Thisisapieceofmetalthatisattachedtotheironcoreoftheelectromagnet.
• A spring: This is attached to the armature and keeps it in place.
• A striker: This is a piece of metal that is attached to the armature.
• A gong :This is a metal plate that is attached to the striker.

Whentheswitchisturnedon,anelectriccurrentflowsthroughtheelectromagnet,magnetizingtheironcore.Themagnetizedcoreattractsthearmature,whichpullsthestrikertowardsthegong.Thestrikerhitsthegong,makingasound.

Assoonasthestrikerhitsthegong,thespringpushesthearmatureback,breakingthecontactbetweenthecoilandthebattery.Theelectromagnetlosesitsmagnetism,andthearmaturespringsbacktoitsoriginalposition.Thecyclethenrepeatsitself,makingthebellringcontinuously.