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# E+M Warmups

Physics is not a discipline, but a way of looking at the world. See if you can use your sense of the world to explain everyday phenomena.

# Electric circuits

Most mobile phones are equipped with a Lithium-ion battery. The battery discharges when used, and needs to be charged regularly.

What change takes place in the battery as it charges?

We have a metal ball and we want to find whether it is positively charged, negatively charged, or electrically neutral.

A positively charged rod is brought close to the ball, and then a negatively charged rod is brought near the ball. In both cases, the ball was attracted to the rod.

What is the charge on the ball?

A resistor is an electric component that resists the flow of current. The above diagram shows two resistors connected in parallel.

What happens to the effective resistance between $$A$$ and $$B$$ if we increase the resistance of $$R_1$$?

A resistor is an electric component that resists the flow of current. The above diagram shows two pairs of resistors: the resistors between $$A$$ and $$B$$ are connected in series, and the resistors between $$C$$ and $$D$$ are connected in parallel.

How should we connect two identical resistors to have a greater effective resistance?

How should we connect 2 identical batteries to maximize the electromotive force (EMF) between the terminals?

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