A standard ammeter must be inserted in series into the circuit (Section 18.9). An induction ammeter has the great advantage of being able to measure currents without making any electrical connection to the circuit. An iron ring is hinged so that it can be snapped around a wire. A coil is wrapped around the iron ring; the ammeter uses the induced emf in the coil to determine the current flowing in the wire.

(a) Does the induction ammeter work equally well for ac and dc currents? Explain.
(b) Can the induction ammeter be placed around both wires connected to an appliance to measure the current drawn by the appliance? Explain.

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Coil Hinge Iron nng Wire