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In a double displacement reaction ______.
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Observe the following diagram and answer the questions.

- Construction of which equipment does the above diagram show?
- On which principle does this equipment work?
- According to which law the coil ABCD rotates?
- Write the law in your own words.
- Where is this equipment used?
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Add potassium chromate (K2CrO4) into the solution of barium sulphate (BaSO4).
- What was the colour of the precipitate formed? Also, write the name of the precipitate.
- Write down the balanced equation for this reaction.
- Will you call this reaction a displacement reaction or a double displacement reaction? Why?
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What is the electronic configuration of K19?
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An element has its electron configuration as 2, 8, 1. Now answer the following questions:
- What is the atomic number of this element?
- What is the group of this element?
- To which period does this element belong?
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Given below is a diagram showing a defect of human eye. Study it and answer the following questions.

(i) Name the defect shown in the figure.
(ii) Give reason for this defect of eye in human being.
(iii) Name the type of lens used to correct the eye defect.
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The device used for producing electric current is called _________.
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Name the following:
Main ore of aluminium.
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When does short circuiting take place?
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What happens to the resistance of the circuit during a short circuit?
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What happens to the flow of electric current during a short circuit?
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What is overloading?
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How can the effects of overloading be avoided?
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In a Std. X class out of 40 students 10 students use spectacles, 2 students have positive power and 8 students have negative power of lenses in their spectacles.
Answer the following questions:
(1) What does the negative power indicate?
(2) What does the positive power indicate?
(3) Generally which type of spectacles do most of the students use?
(4) What defect of eyesight do most of the students suffer from?
(5) Give two possible reasons for the above defect.
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Sodium or potassium salt of higher fatty acid is termed …………
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State Fleming’s right-hand rule.
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State three differences between direct current and alternating current.
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Why should the wires carrying electricity not be touched barefooted?
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Explain two possible reasons of myopia. How can it be corrected? Explain with a suitable diagram.
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