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Chapter 21: Q24CQ (page 772)

Why should you not connect an ammeter directly across a voltage source as shown in Figure21.48?(Note that script Ein the figure stands for emf.)

Short Answer

Expert verified

One should not connect an ammeter directly across a voltage source because it can cause a short circuit.

Step by step solution

01

Short-circuit

When the two terminals of a battery get in direct contact through a wire, when no load is attached to the wire, a large amount of current flows through it. Due to the flow of a large amount of current, the wire burns up, and the circuit breaks. This condition of the circuit is known as a Short circuit.

02

Explanation of why we should not connect an ammeter directly across a voltage source

To measure the current accurately we need an ammeter with the least resistance possible. This means that if we connect an ammeter directly to the circuit, it will offer almost no resistance and will create a condition called short-circuit. This could damage the ammeter.

Therefore, we should not connect an ammeter directly across a voltage source as it causes a short circuit.

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Most popular questions from this chapter

Consider a rechargeable lithium cell that is to be used to power a camcorder. Construct a problem in which you calculate the internal resistance of the cell during normal operation. Also, calculate the minimum voltage output of a battery charger to be used to recharge your lithium cell. Among the things to be considered are the emf and useful terminal voltage of a lithium cell and the current it should be able to supply to a camcorder.

A \(160 - \mu F\)capacitor charged to \(450\;V\)is discharged through a \(31.2 - k\Omega \)resistor. (a) Find the time constant.(b) Calculate the temperature increase of the resistor, given that its mass is \(2.50\;g\)and its specific heat is \(1.67\frac{{kJ}}{{kg{ \cdot ^\circ }C}}\), noting that most of the thermal energy is retained in the short time of the discharge. (c) Calculate the new resistance, assuming it is pure carbon. (d) Does this change in resistance seem significant?

Find the currents flowing in the circuit in Figure 21.47.

Find the currents flowing in the circuit in Figure\(21.52\). Explicitly show how you follow the steps in the Problem-Solving Strategies for Series and Parallel Resistors.

Suppose you measure the terminal voltage of an1.585-V alkaline cell having an internal resistance of0.100Ωby placing arole="math" localid="1656394302991" 1.00-kΩvoltmeter across its terminals. (See Figure 21.54.) (a) What current flows? (b) Find the terminal voltage. (c) To see how close the measured terminal voltage is to the emf, calculate their ratio.
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