Learn Unit IV: Effects of Current with Free Lessons & Tips

The resistance of the bulb can be calculated using Ohm's law: R=V/I=330V/110W=3Ω The energy consumed by three bulbs burning for 5 hours is E=P⋅t=110W×3×5h=1650Wh=1.65kWh The cost in rupees is calculated as Cost=Energy consumed×Rate=1.65kWh×0.70 Rupees/kWh=1.155

The resistance of the copper wire can be calculated using the formula R=ρ⋅l/A, where ρρ is the resistivity of copper, ll is the length of the wire, and AA is the cross-sectional area of the wire. Given ρ=1.72×10−8 Ω⋅mρ=1.72×10−8Ω⋅m, l=2 km=2000 ml=2km=2000m, and r=2 mm=0.002 mr=2mm=0.002m (radius),the cross-sectional area A=πr2=π×(0.002)2 m2A=πr2=π×(0.002)2m2. Substituting these values into the formula gives R=(1.72×10−8 Ω⋅m)×(2000 m)π×(0.002)2 m2R=π×(0.002)2m2(1.72×10−8Ω⋅m)×(2000m). Calculating this expression gives the resistance of the wire.

• Domestic appliances typically use parallel connections. This is because in parallel connections, each appliance gets the full voltage of the power supply, ensuring consistent operation regardless of the other appliances in the circuit. Additionally, if one appliance fails or is turned off, it does not affect the operation of other appliances connected in parallel.

Joule's law states that the heat produced in a resistor is directly proportional to the square of the current passing through it and the resistance of the resistor. Mathematically, H=I²×R, where H is the heat produced, I is the current, and R is the resistance. To find the current, I=P/V and then use Ohm's law to find resistance R=V/I

• A fuse is placed in series with an electrical appliance in a circuit to protect the appliance and the circuit from damage due to excessive current. A fuse with a defined rating should not be replaced by one with a larger rating because a larger-rated fuse may allow too much current to pass through the circuit, risking damage to the appliance and causing a potential fire hazard.

• The frequency of an alternating current (AC) is the number of complete cycles per second and is measured in hertz (Hz). In India, the standard frequency of AC power supply is 50 Hz. Alternating current is considered advantageous over direct current (DC) for long-range transmission of electric energy because it can be easily stepped up or down in voltage using transformers, which allows for efficient transmission over long distances with minimal energy loss.

• An electromagnet is a type of magnet in which the magnetic field is produced by the flow of electric current. To transform a soft iron piece into an electromagnet, a coil of wire is wound around the iron core, and when electric current passes through the coil, it magnetizes the iron core, creating a temporary magnet.

• Induced current in a circuit can be generated by electromagnetic induction, which occurs when a change in magnetic flux through a closed circuit induces an electromotive force (emf) that causes current to flow. This can be achieved by moving a magnet near a coil of wire or by changing the magnetic field strength through the coil.