D.C. Circuits

A fixed resistor of resistance 12 Ω is connected to a battery. There is a current of 0.20 A in the resistor. The current is now doubled.

What is the new power dissipated in the resistor?

• 0.48 W

• 0.96 W

• 1.9 W

• 4.8 W

There is a current in a resistor for an unknown time.

Which two quantities can be used to calculate the energy dissipated by the resistor?

• the current in the resistor and the potential difference across the resistor

• the resistance of the resistor and the current in the resistor

• the total charge passing through the resistor and the potential difference across the resistor

• the total charge passing through the resistor and the resistance of the resistor

Two cells with electromotive forces E₁ and E₂ and internal resistances r₁ and r₂ are connected to a resistor R as shown.

The terminal potential difference across cell 1 is zero.

Which expression gives the resistance of resistor R?

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A battery has an electromotive force (e.m.f.) E and internal resistance r. The battery delivers a current I to a variable resistor and the potential difference (p.d.) across its terminals is V.

The variable resistor is adjusted so that I increases. Why does V decrease?

• The e.m.f. E decreases.

• The internal resistance r increases.

• The p.d. across r increases.

• The resistance of the variable resistor increases.

Three identical resistors are connected between terminals P and Q in different networks X, Y and

Z as shown.

What is the order of increasing combined resistance between P and Q (lowest first)?

• X → Y → Z

• X → Z → Y

• Y → X → Z

• Y → Z → X