Chapter 3 Current Electricity
- 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