Ok, your middle finger is representing the conventional current, so your middle finger should be pointing downwards. Your index finger represents the direction of magnetic field (north pole to south pole), so point index finger towards your laptop screen/page. Now, which way is your thumb pointing at? It will be pointing right, so B would be the answer.
Q14. It's easy to distinguish physical and chemical change by asking a question: Can this reaction be easily reversed? Physical change can be easily reversed, but chemical change can not be easily reversed. Ice melting and water boiling can be easily reversed by just freezing or condensing it, respectively, so it's a physical change. However, burning wood can not be easily reversed, so it's a chemical change. So B.
Q19. When it's neutral, the compound doesn't react with any of them. When the compound is amphoteric, it reacts with both acid and alkali. So A.
Q21. Steel used for drill should wear scratches (hardness). However, it does not necessarily have to be dense or malleable or have high melting point. So B.
Q22. Galvanising does not prevent oxygen from reaching steel. Although oxygen goes through the layer of zinc, because zinc is more reactive than steel, zinc loses electron to be zinc oxide instead of iron (zinc reacts, not iron). So C.
Q23. Nitrogen monoxide is toxic; hence, it is converted to nitrogen and oxygen. So D.
Q31. In order to calculate efficiency, we should know both useful output power and input power. The question already states input power (250W), so we only need to calculate useful output power. Power = Work/Time. Work = Force * Distance.
Power = (Force * Distance)/Time
Hence, (50N*4m)/3s =66.67W. Efficiency is useful output power over input power, so 66.67/250 = 0.267 = 27%, so B.
Q35. Angle of reflection equals to the angle of incidence. The angle of incidence is the angle between the normal and the ray. Hence, the angle would be 90˚-20˚=70˚, so C.
Q38. Rod is rubbed with cloth to be charged, so both should be insulator (When two insulators are rubbed, they become charged according to electron affinity). Negatively charged thread moves towards the rod, so the rod should be positive. So D
Q39. For this question, use a right hand rule or left hand rule depending on what you learnt. Can you reply to this comment which one did you learn?
Ok, your middle finger is representing the conventional current, so your middle finger should be pointing downwards. Your index finger represents the direction of magnetic field (north pole to south pole), so point index finger towards your laptop screen/page. Now, which way is your thumb pointing at? It will be pointing right, so B would be the answer.
I learnt the left hand rule.
Hi, thank you for your question.
Q14. It's easy to distinguish physical and chemical change by asking a question: Can this reaction be easily reversed? Physical change can be easily reversed, but chemical change can not be easily reversed. Ice melting and water boiling can be easily reversed by just freezing or condensing it, respectively, so it's a physical change. However, burning wood can not be easily reversed, so it's a chemical change. So B.
Q19. When it's neutral, the compound doesn't react with any of them. When the compound is amphoteric, it reacts with both acid and alkali. So A.
Q21. Steel used for drill should wear scratches (hardness). However, it does not necessarily have to be dense or malleable or have high melting point. So B.
Q22. Galvanising does not prevent oxygen from reaching steel. Although oxygen goes through the layer of zinc, because zinc is more reactive than steel, zinc loses electron to be zinc oxide instead of iron (zinc reacts, not iron). So C.
Q23. Nitrogen monoxide is toxic; hence, it is converted to nitrogen and oxygen. So D.
Q31. In order to calculate efficiency, we should know both useful output power and input power. The question already states input power (250W), so we only need to calculate useful output power. Power = Work/Time. Work = Force * Distance.
Power = (Force * Distance)/Time
Hence, (50N*4m)/3s =66.67W. Efficiency is useful output power over input power, so 66.67/250 = 0.267 = 27%, so B.
Q35. Angle of reflection equals to the angle of incidence. The angle of incidence is the angle between the normal and the ray. Hence, the angle would be 90˚-20˚=70˚, so C.
Q38. Rod is rubbed with cloth to be charged, so both should be insulator (When two insulators are rubbed, they become charged according to electron affinity). Negatively charged thread moves towards the rod, so the rod should be positive. So D
Q39. For this question, use a right hand rule or left hand rule depending on what you learnt. Can you reply to this comment which one did you learn?
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