9th
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- Write the steps in deducing the chemical formulae of the following compounds. (ii) Potassium nitrate, Potassium nitrate : Step 1 : Write the symbols and valencies of the radicals. Symbols K NO₃ Valency 1 1 Step 2 : Cross-multiply symbols of r... 1
- Write the steps in deducing the chemical formulae of the following compounds. Sodium sulphate Sodium sulphate : Step 1 : Write the symbols and valencies of the radicals. Symbols Na SO₄ Valency 1 2 Step 2 : Cross-multiply symbols of ra... 1
- Write symbols of the following elements and the radicals obtained from them and indicate the charge on the radicals. Element Symbols Charge 1. Mercury Hg Mercurous- Hg⁺ 2. Potassium K Potassium- K⁺ 3. Nitrogen N Azide- N₃⁻ 4. Copper Cu Cuprous- Cu⁺ 5. Sulph... 2
- Give example Trivalent basic radicals Trivalent Basic Radical : (i) Al^(3+ ) (ii) Cr³⁺ (iii) Fe³⁺ (iv) Au³⁺ 1
- give example Bivalent acidic radicals Bivalent Acidic Radical : (i) S^(2- ) (ii) O^(2- ) (iii) Se^(2- ) 2
- Give example Metals with variable valency Metal With Variable Valency : (i) Cu → Cu^(+ )Cu²⁺, (ii) Hg → Hg⁺, Hg²⁺ (iii) Fe → Fe²⁺ , Fe³⁺ 1
- Give example Composite radicals Composite Radical : (i) SO₄^( 2- ) (ii) H₃O⁺ (iii) NH₄^(+ ) (iv) HCO₃^(- ) (v) SO₄^(2- ) (vi) NO₄⁻ 2
- Give examples Basic radicals Basic Radical : (i) Na⁺ (ii) Fe²⁺ (iii) Ag⁺ (iv)^( )Al³⁺ (v) Cr³⁺ (vi) Sn²⁺ 2
- Give examples. Positive ions Positive ions : (i) Sodium Ions Na⁺ (ii) Silver ions Ag⁺ (iii) Aluminium ions^( )Al^(3+ ), (iv) Chromium ion Cr³⁺ (v) Calcium ion Ca²⁺ 1
- Why are fuse wires used? Used to protect domestic appliances, fuse wire has specific melting point and is made of a mixture of substances. It is connected in series... 1
- Explain Ohm’s law with the formula. George Simon Ohm, a German Scientist put across a law known as Ohm’s law, from which the relationship between the current flowing through a... 1
- What are free electrons? Free electrons are the one or more outer shell electrons found in every atom of a metallic conductor, which are bound weakly to the nucleus.... 1
- If a charge of 420 C flows through a conducting wire in 5 minutes what is the value of the current? Current flowing through the conducting wire is I= Charge(Q)/Time (t) ⇒I=420/(5×60)=420/300=1.4 A Hence, the current flowing through the wire... 1
- When two resistors are connected in series, their effective resistance is 80 Ω. When they are connected in parallel, Let the two resistances be R₁ and R₂. Therefore, R₁ + R_(2 )= 80 Ω or, R_(1 )= 80 −R₂-R₂ .....(i) and 1/R₁+1/R₂=1/20 ⇒R₁R₂=20(R₁+R₂) As, R₁=... 1
- The resistance of a 1 m long nichrome wire is 6 Ω. If we reduce the length of the wire to 70 cm. Resistance of a wire is directly proportional to its length. Let R_(1 )and R₂ be the resistances of the nichrome wire at 100 cm (1 m) and 70... 1
- Three resistances x1 , x2 and x3 are connected in a circuit in different ways. x is the effective resistance 1. In this case, x₁,x_(2 )and x_(3 )are connected in series. 2. In this case, x₁ , x_(2 )and x_(3 )are connected in series. 3. In this case,... 1
- Resistances R1 , R2 , R3 and R4 are connected as shown in the figure. S1 and S2 are two keys. (i) The circuit for this case is shown below. R₄ is shunted by S_(2 ). Hence the Resistance of this combination will be practically zero R₁... 1
- The resistance of a conductor of length x is r. If its area of cross-section is a, what is its resistivity? We know R = ρ(L/A) ∴ Resistivity of a conductor, ρ = RA / L Here, L = x, R = r and A = a Therefore, ρ = ra / x The unit of resistivity is oh... 1
- Match the pairs ‘A’ Group ‘B’ Group 1. Free electrons a. V/ R 2. Current b. Increases the resistance in the circuit ‘A’ Group ‘B’ Group 1. Free electrons c. Weakly attached 2. Current a. V/ R 3. Resistivity d. VA/LI 4. Resistances in series b. Increases th... 1
- The following table shows current in Amperes and potential difference in Volts. V (Volts) I (Amp) (i). From Ohm's law, we have R=V/I V (volts) I (amp) R (ohm) 4 9 4/9=0.44 5 11.25 5/11.25=0.44 6 13.5 6/13.5=0.44 Therefore, average resista... 1
- Umesh has two bulbs having resistances of 15 Ω and 30 Ω . He wants to connect them in a circuit, but if he connects When Umesh connects the bulbs one at a time, the filaments of the bulbs get burnt. This means the heat energy generated in the filament is b... 1
- The following figure shows the symbols for components used in the accompanying electrical circuit. Ohm's law I=V/R can be proved with the help of above circuit. 1
- The accompanying figure shows some electrical appliances connected in a circuit in a house. 1. The appliances are in parallel connection. 2. The potential difference across each appliance should be same as they are connected in para... 1
- What is the law of conservation of energy? Energy can neither be created nor destroyed. It can be converted from one form into another. Thus, the total amount of energy in the univers... 1