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A circuit diagram contains a pair of unequal parallel lines, a circle with a cross, and a rectangle. Two circle-with-cross symbols connect between the same junctions P and Q. Which interpretation is correct?
The unequal lines represent a cell, each circle with a cross represents a lamp, the rectangle represents a resistor, and the two lamps are in parallel. The unequal lines represent a resistor, each circle with a cross represents a cell, and the two cells are in series. The unequal lines represent a lamp, the rectangle represents a cell, and the two circle-with-cross symbols are in series. The symbols cannot be identified without knowing their physical sizes, and P and Q do not reveal the arrangement. A student must measure a lamp’s current, its potential difference and then its resistance in a low-voltage classroom circuit. The supply is disconnected whenever connections or leads are changed. Which plan is correct?
Measure current in series and voltage in parallel while powered; then disconnect the supply, isolate the lamp and use resistance mode. Measure current in parallel, voltage in series and resistance while the supply remains connected. Use resistance mode in series for all three measurements without changing terminals or range. Measure both current and voltage in parallel, then calculate resistance without isolating the lamp. Three resistors form one unbranched loop across a 9.0 V source. Which set of observations could be correct?
Each resistor carries 0.40 A, their potential differences are 2.0 V, 3.0 V and 4.0 V, and the total resistance is greater than any one resistor. The resistor currents are 0.40 A, 0.30 A and 0.20 A, while their potential differences sum to 9.0 V. Each resistor carries 0.40 A and has the full 9.0 V across it. Each resistor carries 0.40 A, but the total resistance is smaller than every individual resistance. Two household lamps are independently switched on separate parallel branches. Which statement describes the circuit?
Each active branch has the supply potential difference, the source current is the sum of the branch currents, and adding another active branch decreases effective resistance. The branches divide the supply potential difference equally, and adding another active branch increases effective resistance. The source current is smaller than either branch current because current is consumed at the junction. Opening either switch must stop both lamps because parallel branches cannot operate independently. Two fans are both rated at 12 V. Fan P is rated 6 W and fan Q is rated 18 W. Which interpretation is correct when both operate at their ratings?
The labels state rated potential difference and power, and fan Q transfers electrical energy three times as fast as fan P. The labels are live meter readings, and fan P transfers energy three times as fast as fan Q. The volt values state stored energy, while the watt values state the charge carried each second. Both fans transfer energy at the same rate because their rated potential differences are equal. An electricity bill lists previous and current cumulative meter readings in kWh and a tariff in dollars per kWh. Which method and action are correct?
Subtract the previous reading from the current reading, multiply that energy by the tariff, and switch off an unused appliance to reduce waste. Use the current reading alone, multiply it by the tariff, and leave unused appliances on to avoid restart energy. Subtract the readings to obtain power in kW, divide by the tariff, and change plug colour to reduce waste. Average the two readings, divide by the tariff, and reduce the supply voltage regardless of appliance ratings.
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Before closing the switch in a circuit built from a diagram, which check most directly verifies that the circuit was set up correctly?
Close the switch first and change random wires until the lamp lights. Count the components without checking which junctions they share. Trace each conducting path and compare every component and junction with the diagram. Check only that the apparatus is arranged neatly. Opening one lamp breaks its path but another lamp remains lit. What arrangement does this observation support?
The lamps become parallel only after one lamp is opened. The lamps are on separate parallel branches. The lamps must be in series because both used the same source. The arrangement cannot be inferred from whether the other lamp remains lit. How should a multimeter be connected to measure the voltage across a lamp in an operating circuit?
Select current mode and connect the meter across the lamp. Disconnect the supply and isolate the lamp before measuring its operating voltage. Select voltage mode and connect the meter in parallel across the lamp. Select voltage mode and insert the meter in series with the lamp. Ammeters before and after two series resistors give different steady readings. Which interpretation is best?
Unequal readings prove the circuit is parallel. At least one connection or reading should be checked because steady current should be the same throughout the series path. The first resistor has used up some current. The current must halve after every series resistor. A source supplies 0.60 A to two parallel branches. One branch carries 0.25 A. What current is in the other branch?
A 6.0 V source is connected to two series components. One has 2.5 V across it. What voltage is across the other?
What happens to effective resistance when another resistor is connected in series?
It is unchanged because current is the same in series. It becomes zero because the resistors cancel. It increases. It decreases because there are more components to carry current. What happens to effective resistance when another resistor is connected on a new parallel branch?
It increases because the circuit contains more resistance. It is unchanged because each branch has the same voltage. It becomes the sum of the branch resistances. It decreases. Which information should be read from a label when checking whether a kettle is intended for a 230 V supply and how quickly it transfers energy?
The electricity-bill meter reading and tariff. Only the power rating, because voltage is a live reading. The voltage rating and the power rating. The serial number and manufacture date. A resistive appliance takes a steady power of 920 W at 230 V. What current does it draw?
4.0 W 4.0 A 211 600 A 0.25 A An appliance operates continuously at 500 W for 4.0 h. The energy tariff is $0.30 per kWh. What is its energy charge?
A bill shows a previous meter reading of 6842 kWh and a current reading of 7015 kWh. What usage belongs to this billing period?
173 kWh 7015 kWh 6842 kWh 13 857 kWh Two fans provide the required airflow. Fan A is 45 W and fan B is 70 W. They would run for the same time. Which choice reduces electrical-energy use?
Either fan uses the same energy because both are fans. Run fan B longer so its higher power has time to become efficient. Use fan A because it provides the required service at lower power for the same time. Use fan B because a higher power rating always means less energy is wasted. Two lamps are connected on separate branches between junctions P and Q. Which measurement plan tests the rule for voltage in parallel branches?
Insert an ammeter in series with one branch and call its current reading the voltage of both branches. Connect one voltmeter in series before P and another in series after Q, then add their readings. Open both branches and measure only the resistance of one lamp. Connect a voltmeter across P and Q for each branch in turn and compare both readings with the supply voltage. A home circuit has a kettle and lamp on separate parallel branches. The kettle branch fuse opens. What should happen if the supply and lamp branch remain sound?
The lamp receives zero voltage because the kettle branch now uses the full supply voltage. The lamp becomes a short circuit because every parallel branch must carry equal current. The lamp should continue operating because its branch still forms a complete path across the supply. The lamp must stop because current has to pass through the kettle before reaching it.
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A bench circuit looks different from its circuit diagram, but every component is connected to the same neighbours. Which conclusion is correct?
It must be parallel because the components occupy different positions. The bench circuit corresponds to the diagram because the electrical connections are the same. It cannot correspond because the physical layout must copy the diagram's geometry. It corresponds only if every connecting wire has the same length. Two lamps are connected on separate branches that leave junction P and rejoin at junction Q. How are they arranged?
They are in series because current can pass through both lamps. They are in series because the branches later rejoin. They cannot be classified unless both lamps are identical. They are in parallel. A student wants to measure the resistance of a resistor that is in a powered circuit. Which preparation and measurement procedure is correct?
Keep the supply connected and insert the meter in series on resistance mode. Keep the supply connected and select current mode. Connect across the live supply before selecting any meter function. Open and disconnect the supply, isolate the resistor, then select resistance mode and connect across it. A series circuit carries 0.35 A just after the source. What current passes through a lamp later in the same unbranched loop?
0.70 A It cannot be known without the lamp voltage. 0.35 A 0.175 A Two parallel branches carry 0.18 A and 0.27 A. What is the current from the source?
0.09 A 0.225 A 0.27 A 0.45 A Three series lamps have measured voltages of 1.2 V, 1.8 V and 3.0 V. Which source voltage is consistent with the readings?
Two branches are connected across a 9.0 V source. What voltage is across each complete branch?
18 V across each branch 9.0 V across each branch 4.5 V across each branch 9.0 V shared in proportion to branch current A second identical resistor is added in series with a lamp. Which qualitative prediction is correct?
Effective resistance follows the parallel rule because two resistors are present. The circuit's effective resistance increases. Effective resistance decreases because current passes through two resistors. Effective resistance is unchanged because the resistors are identical. A switch closes an extra resistor branch across a source. Which qualitative change occurs?
The effective resistance of the parallel network decreases. Effective resistance increases because another resistor is now connected. Effective resistance stays fixed because source voltage stays fixed. The network becomes series because the switch is closed. Why are household appliances connected in parallel rather than in series?
Each appliance receives the full supply voltage and can be switched independently. They share the supply voltage and must all be switched together. The same current must pass through every appliance. Adding an appliance increases effective resistance and protects every appliance. An appliance label states ‘230 V, 1200 W’. What do these two values identify?
The two values are live measurements that change every second. Its intended operating voltage is 230 V and its rated power is 1200 W. It used 230 kWh and cost $1200 during the last billing period. Its current is 230 A and its resistance is 1200 Ω. A D.C. device has 12 V across it and draws a steady 2.5 A. What is its electrical power?
A heater operates continuously at 2.0 kW for 3.0 h. Electricity costs $0.28 per kWh. What is its energy charge?
Which line on an electricity bill identifies the household's electrical energy used during the stated billing period?
The appliance voltage rating in volts. The tariff in dollars per kWh. The latest cumulative reading without reference to the previous reading. The usage in kWh, often calculated from current minus previous meter reading. Which action most directly reduces electrical-energy wastage while keeping the same room lit when needed?
Read the appliance label without changing how the light is used. Switch off empty-room lights and use an efficient lamp of suitable brightness. Leave every light on so repeated switching does not use energy. Use a higher-power lamp regardless of the brightness required.
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