標題:
simple electric circuit q
發問:
Why are the following statements incorrect?1) In series circuit, the fact that currents through all components are the same can be explained by the law of conservation of energy.2) In a parallel circuit, the fact that the p.d. across each of the parallel brances is the same can be explained by the law of... 顯示更多 Why are the following statements incorrect? 1) In series circuit, the fact that currents through all components are the same can be explained by the law of conservation of energy. 2) In a parallel circuit, the fact that the p.d. across each of the parallel brances is the same can be explained by the law of conservation of change. 3) A resistor network is equivalent to a resistor if the voltage across the network equals that across the resistor. 更新: 4) When a practical ammeter is used to measure the current through a component, its reading must be smaller than the true current through the component. 更新 2: 5) When a practical voltmeter is used to measure the voltage through a component, its reading must be smaller than the true current through the component. 更新 3: I am sorry. It was a typing mistake for (5). You are right. But could you explain (2)? Why is the p.d. across each of the parallel branches the same? According to my textbook, all the statements here are wrong, is my textbook wrong?
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1. False. It should be the Law of Conservation of Charges. 2. False. 3. False. It is true only if the currents through the network and the resistor are the same. 4. True. The introduction of a practical ammeter adds extra resistance to the circuit, thus lowering the current. 5. I supose there is a typing mistake in the sentence. It should read ".... its reading must be smaller than the true VOLTAGE through the component." If you are really referring to the current, then it doesn't make any sense, as voltmeter is not intended to measure current. Should you refer to the "voltage", then the statement is true. A practical voltmeter needs to draw some current from the circuit, thus lowering the current passing through the component, resulting in a lower measured voltage. 2013-03-22 15:32:07 補充： Your suppl question: 2. It is just the conservation of energy, any unit charge passes through each branch of the circuit releases the same amount of energy as what it (the unit charge) has been obtained from the battery... 2013-03-22 15:32:29 補充： (cont'd)... Since energy = qV (where q is the charge and V is the p.d.), when energies released are the same, all Vs are the same. 2013-03-22 15:35:56 補充： In Q(4) and (5), I am in doubt on the answers given in your book. I cannot figure out any situation where the meter reading is higher than the true value.
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