The battery for a certain cell phone is rated at 3.70 V. According to the manufacturer it can produce 3.15 * 10^4 J of electrical energy, enough for 5.25 h of operation, before needing to be recharged. Find the average current that this cell phone draws when turned on.

A $1.4\text{kW}$ toaster is connected to a wall outlet, which provides a potential difference of $120\mathrm{V}$. What is the effective resistance of the toaster?

A certain resistor is connected across a $9.0\mathrm{V}$ battery and dissipates $20\mathrm{ W}$ of power. The battery is replaced with an $18\mathrm{V}$ battery. How much power is dissipated in the resistor now?

A typical small flashlight contains two batteries, each having an emf of 1.5 V, connected in series with a bulb having resistance 17 Ω. ((b) If the batteries last for 5.0 h, what is the total energy delivered to the bulb?

A typical small flashlight contains two batteries, each having an emf of 1.5 V, connected in series with a bulb having resistance 17 Ω. (a) If the internal resistance of the batteries is negligible, what power is delivered to the bulb?

A heart defibrillator is used to enable the heart to start beating if it has stopped. This is done by passing a large current of 12 A through the body at 25 V for a very short time, usually about 3.0 ms. (b) how much energy is transferred?

Electric eels generate electric pulses along their skin that can be used to stun an enemy when they come into contact with it. Tests have shown that these pulses can be up to 500 V and produce currents of 80 mA (or even larger). A typical pulse lasts for 10 ms. What power and how much energy are delivered to the unfortunate enemy with a single pulse, assuming a steady current?

Consider the circuit of Fig. E25.30

. (c) At what rate is electrical energy being converted to other forms in the 8.0-V battery?

Consider the circuit of Fig. E25.30

. (b) What is the power output of the 16.0-V battery?