Consider the circuits at right. Note that r always denotes the internal resistan
ID: 3278673 • Letter: C
Question
Consider the circuits at right. Note that r always denotes the internal resistance of the battery, and that voltmeters and ammeters are idealized. For each question below, write which circuit (s) match the prompt, and write a very brief explanation why. (a) In which circuit (s) is the ammeter connected correctly to measure the current through the battery? (b) In which circuit (s) is the current through the battery nearly zero? c) In which circuit (s) does the ammeter correctly measure the current through the resistor with resistance R? (d) In which circuit(s) does the voltmeter correctly measure the terminal voltage of the battery? (e) In which circuit (s) does the voltmeter read zero? (f) In which circuit(s) does the ammeter read zero?Explanation / Answer
Generally the voltmeter is added parallel to the component through which we want to know the voltage (potential difference) and an ammeter is added in series to the component through which we want to know the current. The second aspect is that voltmeter has a very high resistance and an ammeter has a very low resistance. Keeping these aspects in mind, the answer to the (a)-(f) are as follows
(a) C, D
(b) A (as the voltmeter has high resistance, there by making the current zero across it)
(c) C, D (to measure the current the ammeter should be added in series and in C and D the ammeter is series to R)
(d) C
(e) D (voltmeter is parallel to zero resistance i.e., to wire so voltage would be zero)
(f) A, B (for the circuit A, the voltmeter is in series with ammeter, i.e., with very high resistance so no current reaches the ammeter to make it non-zero current. In the case of (B) the ammeter is in series with the voltmeter and hence the branch acts like a very high resistance)
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