Class 12 Physics MCQ - AC Generator PDF

[Contact](https://www.sanfoundry.com/contact/) **Class 12 Physics MCQ -- AC Generator** This set of Class 12 Physics Chapter 7 Multiple Choice Questions & Answers (MCQs) focuses on "AC Generator". 1\. A 100 turn coil of area 0.1 m^2^ rotates at half a revolution per second. It is placed in a unif...

[Contact](https://www.sanfoundry.com/contact/) **Class 12 Physics MCQ -- AC Generator** This set of Class 12 Physics Chapter 7 Multiple Choice Questions & Answers (MCQs) focuses on "AC Generator". 1\. A 100 turn coil of area 0.1 m^2^ rotates at half a revolution per second. It is placed in a uniform magnetic field of 0.01 T perpendicular to the axis of rotation of the coil. Calculate the maximum voltage generated in the coil?\ a) 256.33 V\ b) 89.12V\ c) 0.314 V\ d) 3.1455 V\ View Answer Answer: c\ Explanation: The maximum voltage generated in the coil,\ e~0~ = nBAω\ e~0~ = nBA × (2πv)\ e~0~ = 100 × 0.01 × 0.1 × 2π × 0.5\ e~0~ = 0.314 V 2\. An a.c. generator consists of a coil of 1000 turns and cross-sectional area of 3m^2^, rotating at a constant angular speed of 60 rad s^-1^ in a uniform magnetic field 0.04 T. The resistance of the coil is 500Ω. Calculate the maximum current drawn from the generator.\ a) 2500 A\ b) 14.4 A\ c) 6.25 A\ d) 0.55 A\ View Answer Answer: b\ Explanation: e~0~ = nBAω\ e~0~ = 1000 × 0.04 × 3 × 60\ e~0~ = 7200 V.\ The maximum current drawn = e0R=7200500\ I = 14.4 A. 3\. Adithya peddles a stationary bicycle the pedals of which are attached to a 500 turn coil of area 11 m^2^. The coil rotates at half a revolution per second and it is placed in a uniform magnetic field of 20.5 T perpendicular to the axis of rotation of the coil. What is the maximum voltage generated in the coil?\ a) 354035 V\ b) 85000V\ c) 111647 V\ d) 46464 V\ View Answer Answer: a\ Explanation: The maximum voltage generated in the coil,\ e~0~ = nBAω\ e~0~ = nBA × (2πv)\ e~0~ = 500 × 20.5 × 11 × 2π × 0.5\ e~0~ = 345035 V advertisement 4\. Identify the principle behind the working of an a.c. generator.\ a) Eddy currents\ b) Faraday's law\ c) Lenz's law\ d) Electromagnetic induction\ View Answer Answer: d\ Explanation: The working of an a.c. generator is based on the principle of electromagnetic induction. When a coil is rotated about an axis perpendicular to the direction of the uniform magnetic field, an induced emf is produced across it and hence current is set up in it. 5\. An armature coil consists of 30 turns of wire, each of area A = 0.05 m^2^ and total resistance of 10 Ω. It rotates in a magnetic field of 0.15T at a constant frequency of 140π Hz. Determine the value of maximum induced emf produced in the coil.\ a) 1 V\ b) 500 V\ c) 63 V\ d) 43 V\ View Answer Answer: c\ Explanation: e~0~ = nBAω.\ e~0~ = 30 × 0.15 × 0.05 × 2π × (140π)\ e~0~ = 63 V. 6\. In an a.c. generator, electrical energy is converted to mechanical energy by electromagnetic induction.\ a) True\ b) False\ View Answer Answer: b\ Explanation: When a coil is rotated about an axis perpendicular to the direction of the uniform magnetic field, an induced emf is produced across it. In an a.c. generator, mechanical energy is converted to electrical energy by electromagnetic induction. 7\. 'X' is a rectangular coil consisting of a large number of turns of copper wire wound over a soft iron core in an a.c. generator. Identify X.\ a) Slip ring\ b) Armature\ c) Copper brushes\ d) Field magnet\ View Answer Answer: b\ Explanation: A rectangular coil consisting of a large number of turns of copper-wound over a soft iron core is called the armature. The soft iron core is used to increase the magnetic flux. 8\. An a.c. generator consists of a coil of 50 turns and an area 2.5 m^2^ rotating at an angular speed of 60 rad s^-1^ in a uniform magnetic field of 0.3 T between two fixed pole pieces. What is the flux through the coil, when the current is zero?\ a) Maximum\ b) Minimum\ c) Zero\ d) Independent of current\ View Answer Answer: a\ Explanation: The current is zero when the coil is vertical. In this position, flux through the coil is maximum. On the other hand, the current is maximum, when the coil is horizontal. So, when the current is zero, the flux through the coil is maximum. 1\. How many types of spherical refracting surfaces are there?\ a) 2\ b) 3\ c) 4\ d) 5\ View Answer Answer: a\ Explanation: The portion of a refracting medium, whose curved surface forms the part of a sphere, is known as a spherical refracting surface. Spherical refracting surfaces are of two types, namely, convex refracting spherical surface and concave refracting spherical surface. 2\. Which among the following is a portion of a transparent refracting medium bound by one spherical surface and the other plane surface?\ a) Concave mirror\ b) Plane mirror\ c) Lens\ d)Prism\ View Answer Answer: c\ Explanation: Lens is a portion of a transparent refracting medium bound by two spherical surfaces or one spherical surface and the other plane surface. Lenses are divided into two classes, namely, convex lens or converging lens, and concave lens or diverging lens. 3\. X is thicker in the middle than at the edges, whereas, Y is thicker at the edges than in the middle. Identify 'X' and 'Y'.\ a) X = concave lens; Y = convex lens\ b) X = convex lens; Y = concave lens\ c) X = plane lens; Y = convex lens\ d) X = concave lens; Y = plane lens\ View Answer Answer: b\ Explanation: When the lens is thicker in the middle than at the edges, then it is convex lens. When the lens is thicker at the edges than in the middle, then it is concave lens. Therefore, X = convex lens, and Y = concave lens. advertisement 4\. Sign conventions for spherical refracting surface are the same as those for spherical mirrors.\ a) True\ b) False\ View Answer Answer: a\ Explanation: Yes, this is a true statement. Sign conventions for spherical refracting surface are the same as those for spherical mirrors. The only difference is that instead of the pole of the mirror, we use the optical center of a lens. Chemistry 1\. The study of reaction kinetics is called \_\_\_\_\_\_\_\_\_\_. a\) Rate of reaction b\) Mechanism of reaction c\) Factors which affect the rate of reaction d\) All of the mentioned **Answer**: d **Explanation:** Reaction kinetics is the study of reaction rates, mechanisms, and the factors that influence reaction rates. 2\. The reaction rate constant can be defined as the rate of reaction when each reactant's concentration is \_\_\_\_\_\_\_\_\_\_\_. a\) Zero b\) Unity c\) Doubled the initial concentration d\) Infinite **Answer**: b **Explanation:** The reaction rate constant can be defined as the rate of the reaction when all of the reactants' concentrations are unity. The rate of a chemical reaction is quantified by a reaction rate constant, or reaction rate coefficient, k. 3\. Which of the following is the right temperature coefficient (n) expression? a\) n = Rate constant at T + 10°/Rate constant at T° b\) n = Rate constant at T + 20°/Rate constant at T° c\) n = Rate constant at T + 30°/Rate constant at T° d)n = Rate constant at T + 40°/Rate constant at T° **Answer**: a **Explanation:** The effect of temperature on a reaction's pace is commonly stated in terms of the temperature coefficient, which is defined by the equation: Temperature coefficient (n) = T + 10° (308 K) rate constant/T° rate constant (298 K). 4\. When the temperature rises, what happens to the peak of the curve in the Maxwell-Boltzmann distribution graph? a\) Shifts forward and upward b\) Shifts forward and downward c\) Shifts backwards and upward d\) Shifts backwards and downward **Answer**: b **Explanation:** The peak moves ahead but downward as the temperature rises. This is because when the temperature rises, the most probable kinetic energy rises, while the percentage of molecules with the most probable kinetic energy drops. 5\. Plotting a graph between temperature and reaction rates can reveal the temperature dependence of reaction rates. a\) Concentration of reactants and temperature b\) Concentration of products and temperature c\) Rate constant and temperature d\) Rate of catalysis and temperature **Answer**: c **Explanation:** Plotting a graph between rate constant and temperature for various reactions can be used to investigate the temperature dependence of reaction rates. 5\. RNA lacks the nitrogen base of \_\_\_\_\_\_\_ a\) Thymine b\) Cytosine c\) Uracil d\) Adenine **Answer**: a **Explanation**: RNA contains the pyrimidine Uracil, whereas DNA contains Thymine. In RNA, Adenine forms two hydrogen bonds with Uracil, but in DNA, Adenine forms two hydrogen bonds with Thymine. 6\. Lysine is an example of a polar but uncharged amino acid, a\) Serine b\) Aspartate c\) Lysine d\) Arginine **Answer**: a **Explanation**: The amino acids Lysine and Arginine are polar and positively charged. Aspartate, on the other hand, is a polar and negatively charged amino acid. Serine is an uncharged, polar amino acid. 7\. Which of the following chemical classes does not belong to the vast group of carbohydrates? a\) Polyhydroxy ketones b\) Polyhalo aldehydes c\) Polyamino aldehydes d\) Polyhydroxy carboxylic acids **Answer**: a **Explanation**: The OH group is absent from polyamino and polyhalo aldehydes. There is no CHO or keto group in polyhydroxy carboxylic acids. When they are hydrolyzed, they do not form OH substituted compounds. 8\. Which of the following statements about metabolism is false? a\) It is due to this process that biomolecules do not have a turnover b\) It involves the formation of biomolecules c\) It involves the breaking down of biomolecules d\) It involves various chemical reactions **Answer**: a **Explanation**: Metabolism entails the breakdown of biomolecules as well as the creation of new ones. It entails a number of chemical processes. It is in charge of the biomolecule turnover. 9\. How can we make an amine from an amino acid? a\) Addition of carbon dioxide b\) Removal of ammonia c\) Addition of ammonia d\) Removal of carbon dioxide **Answer**: d **Explanation**: The elimination of a molecule of carbon dioxide transforms an amino acid into an amine. This is an example of a metabolic reaction that involves the conversion of one biomolecule into another. 10\. When converting a disaccharide to monosaccharides, which bond is hydrolyzed? a\) Disulfide bond b\) Glycosidic bond c\) Phosphodiester bond d\) Hydrogen bond **Answer**: b Biology **1. If a hybrid expresses a character, it is called \_\_\_\_\_\_\_\_\_ ** 1. Epistasis 2. Dominant 3. Co-dominant 4. Recessive **2. A plant having the genotype AABbCC will produce \_\_\_\_\_\_ kinds of gametes** 1. 5 2. 4 3. 3 4. 2 **3. Colour blindness is an \_\_\_\_\_\_\_\_\_ linked recessive trait** 1. Z chromosome 2. Y chromosome 3. X chromosome 4. None of the above **4.** **In most species, mitochondrial DNA is passed down from ** 1. DNA 2. Mother and Father 3. Father 4. Mother **5. Where are the genes for cytoplasmic male sterility in plants located?** 1. Chloroplast genome 2. Mitochondrial genome 3. Cytosome 4. None of the above **6. \_\_\_\_\_\_\_\_\_ is a type of trait whose phenotype is influenced by more than one gene** 1. Oncogenic Trait 2. Monogenic trait 3. Polygenic trait 4. None of the above **7. An individual's collection of genes is called \_\_\_\_\_\_** 1. Genotype 2. Phenotype 3. Trait 4. None of the above **8. A man marries a woman and both do not show any apparent traits of inherited disease. Five sons and two daughters are born, and three of their sons suffer from a disease. However, none of the daughters is affected. The following mode of inheritance for the disease is** 1. Sex-linked recessive 2. Sex-linked dominant 3. Autosomal dominant 4. None of the above **9. A trait that "overpowers" and hide another trait is called** 1. Overpowering trait 2. Complex trait 3. Recessive trait 4. Dominant Trait **10. Why is haemophilia a disease that is more commonly seen in males?** 1. Both (2) and (3) 2. The disease is Y- linked 3. The disease is X- linked 4. None of the above   Human Health And Disease MCQ ---------------------------- **1. Immunosuppressants such as \_\_\_\_\_\_\_\_\_ prevent transplanted organs from being rejected in recipients.** 1. Thrombin 2. Cyclosporine 3. Aspirin 4. None of the above **2. Both B & T lymphocytes are produced in the bone marrow; however, only the T lymphocytes travel to the \_\_\_\_\_\_ and mature there.** 1. Spleen 2. Thymus 3. Pituitary gland 4. Adrenal gland **3. The \_\_\_\_\_\_\_\_\_ is at its largest in children, but with the onset of puberty, it eventually shrinks and gets replaced by fat.** 1. Thymus 2. Hypothalamus 3. Parathyroid gland 4. None of the above **4. Ascaris lumbricoides is a species of parasitic roundworm that lives in \_\_\_\_\_\_\_\_\_.** 1. Humans 2. Grasshoppers 3. Pigs 4. None of the above **5. Which of the following diseases has been eradicated?** 1. Smallpox 2. Rinderpest 3. Polio 4. All of the above **6. A kind of an injury or damage, which results in the premature death of all the nearby cells in a tissue or an organ through autolysis is called \_\_\_\_\_\_\_.** 1. Neurosis 2. Necrosis 3. Apoptosis 4. Cellular senescence **7. Hypochondria is also termed as\_\_\_\_\_\_\_.** 1. Health anxiety 2. Sleep apnea 3. Hypnagogia 4. Narcolepsy **8. The immune system comprises\_\_\_\_\_\_\_.** 1. Humoral and fibrous systems 2. Humoral and Cell-mediated systems 3. Antigens 4. Lymphocytes **9. Which of the following is a viral disease?** 1. Diphtheria 2. Filariasis 3. Leprosy 4. Influenza **10. Carcinoma arises from the\_\_\_\_\_\_\_.** 1. Epithelial cells 2. Bone Marrow 3. Pigment containing Cells 4. None of the above **11. Melanoma is a type of cancer that develops from \_\_\_\_\_\_\_.** 1. Granulocytes 2. Melanocytes 3. Adipocyte 4. None of the above **12. Human Immunodeficiency Virus causes aids by attacking a type of white blood cell called\_\_\_\_\_\_\_.** 1. CD4 2. CD3 3. CD8 4. None of the above **13. Plague is caused by the bacterium \_\_\_\_\_\_\_.** 1. Yersinia pseudotuberculosis 2. Yersinia pestis 3. Yersinia enterocolitica 4. None of the above **14. Elephantiasis is caused by \_\_\_\_\_\_\_.** 1. Filarial worms 2. Flatworms 3. Tapeworms 4. None of the above **15. \_\_\_\_\_\_\_\_\_\_\_ is an example of a stimulant.** 1. Lorazepam 2. Amphetamine 3. Oxazepam 4. Phencyclidine