Question

By a cell a current of 0.9 A flows through 2 ohm resistor and 0.3 ohm through 7 ohm resistor the internal resitance of the cell​

Answer 1

41. The heating element of a clothes drier has a resistance of 11 W and is connected across a 240 V electrical outlet. What is the current in the heating element? (22 A) V = IR ∴ I = 240 11 = 21.8 A . 42. Three resistors, 25 W , 45 W and 75 W are connected in series, and a 0.51 A current passes through them. What is (a) the equivalent resistance and (b) the total potential difference across the three resistors? (145 W ; 74 V) (a) Req = R1 + R2 + R3 = 25 + 45 + 75 = 145 W . (b) V = IR = 0.51 × 145 = 74 V . 43. The current in a series circuit is 15.0 A . When an additional 8.00 W resistor is inserted in series, the current drops to 12.0 A . What is the resistance in the original circuit? (32 W) V = IR = 15.0 × R = 12.0 × (R + 8.0) which gives R = 32 W . 44. Suppose you want to run some apparatus that is 200 m from the plug point. Each of the two wires connecting the apparatus to the 240 V supply has a resistance per unit length of 0.006 W m−1 . If the apparatus draws a current of 5.0 A , what will be the voltage drop across the lead, and what voltage will be applied to your apparatus? (12 V ; 228 V) The total length of the wires to and from the apparatus is 200×2 = 400 m . The total resistance of the lead is therefore 400 × 0.006 = 2.4 W . Using Ohm’s law we find that the voltage drop across the lead V = IR = 5.0 × 2.4 = 12 V . Since the lead is in series with the apparatus, the voltage drop across the apparatus must be The voltage of the supply minus the voltage drop across the leads. Thus V = 240−12 = 228 V . 45. The element of an electric oven is designed to produce 3.0 kW of heat when connected to a 220 V source. What must be the resistance of the element? (16.1 W) P = V 2 R , hence R = V 2 P = 2202 3 × 103 = 16.1 W . 46. A car starter motor draws 150 A from the 12 V battery. How much power is this? (1.8 kW) P = V I = 12 × 150 = 1800 W. 47. How many kWh does a 1500W electric fry