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Multiple choice physics electric current and its effects coil and fuse heating effect of electric current- uses applications of heating effect of electric current

Thermal energy produced by the resistance R in time duration 1 $ \mu s $. using the source at resonance condition is 

  1. 0 J
  2. $ 1 \mu J $
  3. $ 100 \mu J $

  4. not possible to calculate from the given information.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

To calculate thermal energy produced by resistance, we need the current through the resistance, which requires knowledge of the circuit components (voltage source, impedance at resonance, circuit configuration). The question states 'using the source at resonance condition' but provides no numerical values for voltage, current, resistance, frequency, or circuit parameters. Without this information, the energy cannot be calculated.

Multiple choice physics electric current and its effects coil and fuse heating effect of electric current- uses applications of heating effect of electric current

Current through resistor of resistance $R$ varies with time as $I = I _ot$. What will be the time taken to deliver heat $H$ by this resistor?

  1. $\left( \cfrac { H } { I _ { 0 } R } \right) ^ { 1 / 2 }$
  2. $\left( \cfrac { H } { 3 I _ { 0 } ^ { 2 } R } \right) ^ { 1 / 3 }$
  3. $\left( \cfrac { 3 H } {I _ { 0 } ^ { 2 } R } \right) ^ { 1 / 3 }$
  4. $\left( \cfrac { H } { I _ { 0 } ^ { 2 } R } \right) ^ { 1 / 3 }$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Heat produced is H = ∫I²R dt. Given I = I₀t, we have H = ∫(I₀t)²R dt from 0 to T. This gives H = I₀²R∫t²dt = I₀²R(T³/3). Solving for time T: T³ = 3H/(I₀²R), so T = (3H/(I₀²R))^(1/3). This matches option C.

Multiple choice physics electric current and its effects coil and fuse heating effect of electric current- uses applications of heating effect of electric current

If p.d. across a conductor is constant and resistivity of its material is $\rho $, the joule heat produced in 1 s is proportional to .. 

  1. $\dfrac{1}{\rho }$
  2. $\dfrac{1}{{\sqrt \rho }}$
  3. $\rho $
  4. ${{\rho ^2}}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Joule heat in 1 second is H = V²/R (since P.d. is constant). Resistance of a conductor is R = ρL/A, where L is length and A is cross-sectional area. For a fixed geometry (L and A constant), R ∝ ρ. Therefore H = V²/R ∝ 1/R ∝ 1/ρ. The heat produced is inversely proportional to resistivity.

Multiple choice physics electric current and its effects coil and fuse heating effect of electric current- uses applications of heating effect of electric current

A coal based thermal power plant producing electricity operates between the temperatures $27^o C$ and $227^o C$ The plant works at 80% of its maximum theoretical efficiency. Complete burring of 1 kg of coal yields 3600 KJ of heat. A house needs 10 units of electricity each day. Coal used for supplying the amount of energy for the house in one year is 

  1. 1141 kg

  2. 580 kg

  3. 605 kg

  4. 765 kg
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Carnot efficiency: η_max = 1 - T_c/T_h = 1 - 300/500 = 0.4. Actual efficiency at 80%: η = 0.4 × 0.8 = 0.32. Yearly electricity needed: 10 × 365 = 3650 units. Each unit requires energy. With 3600 kJ/kg coal and 32% efficiency, usable energy per kg = 3600 × 0.32 = 1152 kJ/kg. Converting units to kJ and calculating: Coal needed ≈ 3650 × (energy per unit in kJ)/(1152) ≈ 580 kg after unit conversions.

Multiple choice physics electric current and its effects coil and fuse heating effect of electric current- uses applications of heating effect of electric current

Two equal resistance when connected in series to a battery, consume electri power  of 60 w.  If these resistnce are now  connected in parallel combination to  the same battery the electric power consumed will be 

  1. 60 W

  2. 240 W

  3. 30 W

  4. 120 W
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

When two equal resistors of resistance R are in series, the equivalent resistance is 2R and power is V^2 / (2R) = 60 W. When connected in parallel, the equivalent resistance is R/2, so the power becomes V^2 / (R/2) = 4 * (V^2 / 2R) = 4 * 60 W = 240 W.

Multiple choice physics electric current and its effects coil and fuse heating effect of electric current- uses applications of heating effect of electric current

Why filament of electric bulb is made of tungsten

  1. Melting Point of filament is very high

  2. Resistance of filament is very less

  3. Both

  4. None
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The resistance of filament should be high so that it can produce heat and light and its melting point should also be high so that it does not melt at the high temperature at which it is producing light.


Answer-(A)

Multiple choice physics electric current and its effects coil and fuse heating effect of electric current- uses applications of heating effect of electric current

The operating temperature of the filament of lamp is ${ 2000 }^{ 0 }C$. The temperature coefficient of the material of filament is ${ 0.005 }^{ 0 }{ C }^{ -1 }$. If the atmospheric temperature is ${ { 0 }^{ 0 }C }$, then the current in the 100W-200W lamp when it is switched on is nearest to 

  1. 2.5 A

  2. 3.5 A

  3. 4.5 A

  4. 5.5 A
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The resistance of the filament varies with temperature. At operating temperature (2000°C), R_hot = V²/P = 220²/100 = 484Ω. Using the temperature coefficient formula: R_cold = R_hot/(1 + α(2000-0)) = 484/(1 + 0.005×2000) = 484/11 = 44Ω. Initial current = V/R_cold = 220/44 = 5A. However, this is an approximation - the actual surge current depends on how quickly the filament heats up. Given the options, 4.5A is the closest reasonable estimate.

Multiple choice physics current electricity electric cells and batteries

Which is not different between primary and secondary cell ?

  1. Reversibility of chemical reaction

  2. Rechargability of cell

  3. Supply of energy to external circuit

  4. Strength of current
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Both primary and secondary cells serve the purpose of supplying energy to external circuit. Chemical reactions are reversible and cell is rechargeable for only secondary cells.  Strength of current in primary cell is low and in secondary cell can be high or low.