Doubtly
@Doubtly · Joined Feb 2021
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- Two long and parallel straight wires A and B carrying currents of 8.0 A and 5.0 A I₁ = 8.0 A I₂ = 5.0 A r = 4.0 cm = 4.0 x 10^(-2 )m l = 10 cm = 0.1 m F = frac2 × 10⁻⁷ I₁ I₂ lr = frac2 × 10⁻⁷ × 8 × 5 × 0.14 × 10⁻² = 2 x 10... 1
- A 3.0 cm wire carrying a current of 10 A is placed inside a solenoid perpendicular to its axis I = 3.0 cm = 3.0 x 10⁻² m I = 10 A B = 0.27 T F = BIl = 0.27 x 10 x 3 x 10⁻² = 8.1 x 10⁻² N 1
- What is the magnitude of magnetic force per unit length on a wire carrying a current of 8 A and making an angle I = 8A, B = 0.15 T and θ = 30° F = BI1 sin θ Therefore, force per unit length on the wire, F = 0.15 × 8 x 1 x sin30° = 0.15 x 8 x 1 x 0.5 =... 1
- A horizontal overhead power line carries a current of 90 A in east to west direction. I = 90 A, r = 1.5 m B = fracμ₀ I2 π r = frac4 π × 10⁻⁷ × 902 π × 1.5 = 1.2 x 10⁻⁵ T (South) 1
- A long straight wire in the horizontal plane carries a current of 50 A in north to south direction. Give the magnitude I = 50 A, r = 2.5 m B = fracμ₀ I2 π r = frac4 π × 10⁻⁷ × 502 π × 2.5 = 4 x 10⁻⁶ T upwards. (due to the wire alone) 1
- A long straight wire carries a current of 35 A. What is the magnitude of the field B at a point 20 cm from the w ire? I = 35 A, r = 20 cm = 20 x 10⁻² m B = fracμ₀ I2 π r = frac4 π × 10⁻⁷ × 352 π × 20 × 10⁻² = 3.5 x 10^(-5 )T 1
- A circular coil of wire consisting of 100 turns, each of radius 8.0 cm carries a current of 0.40 A. n = 100, I = 0.40 A, r = 8.0 cm = 8.0 x 10⁻² m B = fracμ₀ nI2 r = frac4 π × 10⁻⁷ × 100 × 0.42 × 8 × 10⁻² = π x 10^(-4 )T 1
- What do you mean by the steady current? A steady current is that in which the intensity of current remains constant. 1
- What do you mean by the varying current? A varying current is the one in which the intensity of current does not remain constant. 1
- Why does current become a scalar quantity? Currently does not obey vector addition principle, i.e., the sum of currents always remains the same, whatever be the angle between conducto... 1
- The free electrons inside a metallic conductor are in random motion. Can we detect current in the conductor? No. In random motion, the average velocity is zero. 2
- What is the essential condition for current flow in a conductor? When a potential difference is applied across the conductor, an electric field is set up and electrons begin to make directed flow and hence... 1
- How can you produce a net flow of electric charges [electric current] in a conductor? By applying a p.d. Under the action of the electric field applied, electrons make drift motion and this produces current. 1
- In the electric field, what happens to the motion of the electrons? Electrons flow in a direction opposite to the electric field. 1
- Why is an ammeter connected in series and a voltmeter in parallel? Ammeter is a low resistance instrument. Hence if ammeter is put in series, it allows the entire current to flow through it and we can measur... 2
- What is the variation of resistivity with temperature? Resistivity, ρ = ρ₀(1 + α t) for conductors where ‘ α ’ is the temperature coefficient of resistance and ‘t’ the temperature change. So resi... 1
- What is superconductivity? In 1911, the Dutch Physicist, Kamerlingh Onnes established experimentally that certain metals and alloys lose their resistance at a very low... 1
- How can you define temperature coefficient of resistance? Temperature coefficient of resistance is defined as the ratio of increase in resistance to the original resistance per degree rise of temper... 1