This physics problem tests your understanding of fundamental physical laws and their applications. The step-by-step solution below breaks down the problem using relevant equations and physical reasoning.
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Here are the solutions to the electricity problems: a) (i) Name the meters A and V. Meter A is an ammeter*. Meter V is a voltmeter*. a) (ii) Calculate the readings of meters A and V when the key K is open. When the key K is open, the circuit is incomplete, and no current can flow. Step 1: Determine the current reading. Since the circuit is open, no current flows through the ammeter A. Reading of A = 0 A Step 2: Determine the voltage reading. With no current flowing through the 2 resistor, there is no potential difference across it (V=IR). Reading of V = 0 V a) (iii) Calculate the reading of meters A and V when K is closed. When the key K is closed, the 10 and 5 resistors are in parallel, and this combination is in series with the 2 resistor. The total voltage supplied by the battery is 12 V. Step 1: Calculate the equivalent resistance of the parallel combination (10 and 5 ). (1)/(R_p) = (1)/(10 ) + (1)/(5 ) (1)/(R_p) = (1)/(10 ) + (2)/(10 ) = (3)/(10 ) R_p = (10)/(3) ≈ 3.33 Step 2: Calculate the total resistance of the circuit. The parallel combination is in series with the 2 resistor. R_total = R_p + 2 R_total = (10)/(3) + 2 = (10)/(3) + (6)/(3) = (16)/(3) ≈ 5.33 Step 3: Calculate the total current flowing through the circuit (reading of ammeter A) using Ohm's Law (I = (V)/(R)). I_A = 12 V(16)/(3) = (12 × 3)/(16) A = (36)/(16) A = (9)/(4) A I_A = 2.25 A The reading of meter A is 2.25 A. Step 4: Calculate the potential difference across the 2 resistor (reading of voltmeter V) using Ohm's Law (V = IR). The total current I_A flows through the 2 resistor. V_V = I_A × 2 V_V = (9)/(4) A × 2 = (18)/(4) V = (9)/(2) V V_V = 4.5 V The reading of meter V is 4.5 V. b) In a modern power socket, there are three cable terminals. One of the cables carries a switch and fuse. Name the three cables and specify the one which each of fuse and switch is connected to. The three cables are: Live wire, Neutral wire, and Earth wire*. The fuse and the switch are both connected to the Live wire. c) (i) What is the equivalence of 1 kWh in joules? Step 1: Convert kilowatts to watts and hours to seconds. 1 kWh = 1 kilowatt × 1 hour 1 kW = 1000 W 1 hour = 3600 seconds Step 2: Calculate the energy in joules. 1 kWh = 1000 W × 3600 s 1 kWh = 3,600,000 J 1 kWh = 3.6 × 10^6 J The equivalence of 1 kWh in joules is 3.6 × 10^6 J. c) (ii) On an electric cooker is marked 4000 W. Find the cost of using this cooker 5 hours daily for 30 days, if electricity cost 55 Frs. per unit. Step 1: Convert the power of the cooker from watts to kilowatts. P = 4000 W = 4 kW Step 2: Calculate the total time the cooker is used in hours. Total time = 5 hours/day × 30 days = 150 hours Step 3: Calculate the total energy consumed in kilowatt-hours (kWh). E = P × Total time E = 4 kW × 150 hours = 600 kWh Step 4: Calculate the total cost. The cost per unit is 55 Frs. and 1 unit is 1 kWh. Total cost = Energy consumed × Cost per unit Total cost = 600 kWh × 55 Frs./kWh = 33,000 Frs. The cost of using the cooker is 33,000 Frs.. That's 2 down. 3 left today — send the next one.