(i) The circuit diagram is shown in figure. Total resistance, R = 1Ω + 2Ω = 3Ω Potential difference, V = 6 V Power used in 2Ω resistor = I2R = (2)2 x 2 = 8 W (ii) The circuit diagram for this case is shown : Power used in 2 resistor = v2R =422 = 8 W. Hence, in both the cases power remains same as 8WRead more
(i) The circuit diagram is shown in figure.
Total resistance, R = 1Ω + 2Ω = 3Ω
Potential difference, V = 6 V
Power used in 2Ω resistor = I2R = (2)2 x 2 = 8 W
(ii) The circuit diagram for this case is shown :
Power used in 2 resistor = v2R =422 = 8 W.
Hence, in both the cases power remains same as 8W.
Power of first lamp (P1) = 100 W Potential difference (V) = 220 V I=P/V= 100/220A= 0.455A Resistance of lamp 1= V/I= 220/(100/220)= 484ohm. Therefore, 𝐼2=𝑃2/𝑉=60/220A=0.273A So, the net current drawn from the supply is given by 𝐼=𝐼1+𝐼2=0.455+0.273=0.728 𝐴
Power of first lamp (P1) = 100 W
Potential difference (V) = 220 V
I=P/V= 100/220A= 0.455A
Resistance of lamp 1= V/I= 220/(100/220)= 484ohm.
Therefore,
𝐼2=𝑃2/𝑉=60/220A=0.273A
So, the net current drawn from the supply is given by
𝐼=𝐼1+𝐼2=0.455+0.273=0.728 𝐴
Energy consumed by an electrical appliance is given by the expression, H = Pt Where, Power of the appliance = P Time = t Energy consumed by a TV set of power 250 W in 1 h = 250 × 3600 = 9 × 105 J Energy consumed by a toaster of power 1200 W in 10 minutes = 1200 × 600 = 7.2× 105 J Therefore, the enerRead more
Energy consumed by an electrical appliance is given by the expression,
H = Pt
Where,
Power of the appliance = P
Time = t
Energy consumed by a TV set of power 250 W in 1 h = 250 × 3600 = 9 × 105 J
Energy consumed by a toaster of power 1200 W in 10 minutes = 1200 × 600
= 7.2× 105 J
Therefore, the energy consumed by a 250 W TV set in 1 h is more than the energy consumed by a toaster of power 1200 W in 10 minutes.
Rate of heat produced by a device is given by the expression for power as P = I2R Where, Resistance of the electric heater, R = 8 Ω Current drawn, I = 15 A P = (15)2 x 8 = 1800 J/s Therefore, heat is produced by the heater at the rate of 1800 J/s.
Rate of heat produced by a device is given by the expression for power as
P = I2R
Where,
Resistance of the electric heater, R = 8 Ω
Current drawn, I = 15 A
P = (15)2 x 8 = 1800 J/s
Therefore, heat is produced by the heater at the rate of 1800 J/s.
(i) The tungsten is used almost exclusively for filament of electric lamps because it has a very high melting point (3300°C). On passing electricity through tungsten filament, its temperature reaches to 2700°C and it gives heat and light energy without being melted. (ii) The conductors of electric hRead more
(i) The tungsten is used almost exclusively for filament of electric lamps because it has a very high melting point (3300°C). On passing electricity through tungsten filament, its temperature reaches to 2700°C and it gives heat and light energy without being melted.
(ii) The conductors of electric heating devices such as bread-toasters and electric irons, are made of an alloy rather than a pure metal because the resistivity of an alloy is much higher than that of pure metal and an alloy does not undergo oxidation (or burn) easily even at high temperature.
(iii) The series arrangement is not used for domestic circuits because in series circuit, if one electrical appliance stops working due to some defect, than all other appliances also stop working because the whole circuit is broken.
(iv) The resistance of a wire is inversely proportional to its area of cross-section, i.e., Resistance R ∝ (1/πr2). If the area of cross section of a conductor of fixed length is increased, then resistance decreases because there are more free electrons for movement in conductor.
(v) Copper and aluminium wires usually employed for electricity transmission because they have very low resistances. So, they do not become too hot on passing electric current.
Compare the power used in the 2 ohm resistor in each of the following circuits:
(i) The circuit diagram is shown in figure. Total resistance, R = 1Ω + 2Ω = 3Ω Potential difference, V = 6 V Power used in 2Ω resistor = I2R = (2)2 x 2 = 8 W (ii) The circuit diagram for this case is shown : Power used in 2 resistor = v2R =422 = 8 W. Hence, in both the cases power remains same as 8WRead more
(i) The circuit diagram is shown in figure.
Total resistance, R = 1Ω + 2Ω = 3Ω
Potential difference, V = 6 V
Power used in 2Ω resistor = I2R = (2)2 x 2 = 8 W
(ii) The circuit diagram for this case is shown :
Power used in 2 resistor = v2R =422 = 8 W.
Hence, in both the cases power remains same as 8W.
See lessTwo lamps, one rated 100 W at 220 V, and the other 60 W at 220 V, are connected in parallel to electric mains supply. What current is drawn from the line if the supply voltage is 220 V?
Power of first lamp (P1) = 100 W Potential difference (V) = 220 V I=P/V= 100/220A= 0.455A Resistance of lamp 1= V/I= 220/(100/220)= 484ohm. Therefore, 𝐼2=𝑃2/𝑉=60/220A=0.273A So, the net current drawn from the supply is given by 𝐼=𝐼1+𝐼2=0.455+0.273=0.728 𝐴
Power of first lamp (P1) = 100 W
Potential difference (V) = 220 V
I=P/V= 100/220A= 0.455A
Resistance of lamp 1= V/I= 220/(100/220)= 484ohm.
Therefore,
𝐼2=𝑃2/𝑉=60/220A=0.273A
So, the net current drawn from the supply is given by
See less𝐼=𝐼1+𝐼2=0.455+0.273=0.728 𝐴
Which uses more energy, a 250 W TV set in 1 hr, or a 1200 W toaster in 10 minutes?
Energy consumed by an electrical appliance is given by the expression, H = Pt Where, Power of the appliance = P Time = t Energy consumed by a TV set of power 250 W in 1 h = 250 × 3600 = 9 × 105 J Energy consumed by a toaster of power 1200 W in 10 minutes = 1200 × 600 = 7.2× 105 J Therefore, the enerRead more
Energy consumed by an electrical appliance is given by the expression,
H = Pt
Where,
Power of the appliance = P
Time = t
Energy consumed by a TV set of power 250 W in 1 h = 250 × 3600 = 9 × 105 J
Energy consumed by a toaster of power 1200 W in 10 minutes = 1200 × 600
= 7.2× 105 J
Therefore, the energy consumed by a 250 W TV set in 1 h is more than the energy consumed by a toaster of power 1200 W in 10 minutes.
See lessAn electric heater of resistance 8 W draws 15 A from the service mains 2 hours. Calculate the rate at which heat is developed in the heater.
Rate of heat produced by a device is given by the expression for power as P = I2R Where, Resistance of the electric heater, R = 8 Ω Current drawn, I = 15 A P = (15)2 x 8 = 1800 J/s Therefore, heat is produced by the heater at the rate of 1800 J/s.
Rate of heat produced by a device is given by the expression for power as
P = I2R
Where,
Resistance of the electric heater, R = 8 Ω
Current drawn, I = 15 A
P = (15)2 x 8 = 1800 J/s
Therefore, heat is produced by the heater at the rate of 1800 J/s.
See lessExplain the following
(i) The tungsten is used almost exclusively for filament of electric lamps because it has a very high melting point (3300°C). On passing electricity through tungsten filament, its temperature reaches to 2700°C and it gives heat and light energy without being melted. (ii) The conductors of electric hRead more
(i) The tungsten is used almost exclusively for filament of electric lamps because it has a very high melting point (3300°C). On passing electricity through tungsten filament, its temperature reaches to 2700°C and it gives heat and light energy without being melted.
See less(ii) The conductors of electric heating devices such as bread-toasters and electric irons, are made of an alloy rather than a pure metal because the resistivity of an alloy is much higher than that of pure metal and an alloy does not undergo oxidation (or burn) easily even at high temperature.
(iii) The series arrangement is not used for domestic circuits because in series circuit, if one electrical appliance stops working due to some defect, than all other appliances also stop working because the whole circuit is broken.
(iv) The resistance of a wire is inversely proportional to its area of cross-section, i.e., Resistance R ∝ (1/πr2). If the area of cross section of a conductor of fixed length is increased, then resistance decreases because there are more free electrons for movement in conductor.
(v) Copper and aluminium wires usually employed for electricity transmission because they have very low resistances. So, they do not become too hot on passing electric current.