A student built an electric circuit that consists of an ideal battery, a voltmeter with resistance R_{V}, an ammeter with resistance R_{A} and a resistor R. She connected all elements in the circuit as shown in Fig. (1). The voltmeter showed a reading of 1V and the ammeter showed a current of 1A. Then, another student switched between the voltmeter and ammeter Fig. (2). As a result, the voltmeter showed the reading of 2V and the ammeter showed the current of 0.5A. What is the resistance of the resistor?

# Electricity & Magnetism.

# STAR connection

Three batteries have their negative terminals connected together.

Find the voltage read by an ideal voltmeter.

# A rod carries a charge uniformly distributed along its length

A rod of length L carries a charge Q uniformly distributed along its length.

Find the electrical field at point P on the axis of the rod, a distance a away from the end of the rod.

# The rod is “flying” above the cable

A conducting rod of length l, mass m, and resistance R is suspended by two vertical conducting wires of lengths d each. The circuit consists of a battery ε, the horizontal fixed wires, two parallel vertical wires , and the conducting rod. All conducting wires have negligible resistance and mass. There is a conducting long cable. The cable is below the rod and at a distance x.

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# When the fuse blows

A fuse is a device to avoid the flow of a large current in a circuit. The potential difference across the fuse is negligible. In our circuit, the maximum current allowed through the fuse is 10 A. The light bulbs marked 40 Watt, 110 V. The bulbs connected to a voltage source of 110 V. What is the maximum number of bulbs that can be placed in parallel before the fuse blows?

# A charged solid spherical conductor with a charged solid spherical shell

A solid spherical conductor has charge + Q and radius R. It is surrounded by a solid spherical shell with charge − Q, inner radius 2R, and outer radius 3R. The objects are isolated in space and the electric potential is zero as the distance from the spheres approaches infinity. Point A is at the center of the inner sphere, Point B is located at R, Point C is located at 2R and point D is located at 3R. All distances are from the center of the inner sphere.

Where is the electric potential maximum?

Where is the electric field maximum?

# The light bulbs are connected in series or parallel

Two identical light bulbs are connected to identical batteries in two different ways. First they are connected in series and then in parallel. In which circuit will the bulbs shine brightly? What is the ratio of the power supplied in series to the power supplied in parallel?