Formulas

Question 1

Charging power

Answer 1

Charging power from the battery (watts)

P = V (battery) x I

Question 2

Pacemaker energy formula

Answer 2

Voltage squared (in volts) x pulse width (in ms) / R (impedance in ohms)

Energy: total stored electrical energy
Energy = V (voltage) x Ah (amp hours)

Question 3

Power formula

Answer 3

How much electrical energy is being used

If voltage and current are known:
P (power in watts) = V (voltage in volts) x I (current in amps)

If current and resistance are known:
P (power in watts) = I (current in amps) squared x R (resistance in ohms)

If voltage and resistance are known:
P (power in watts) = V (voltage in volts) squared x R (resistance in oh

Question 4

Ohm’s Law

Answer 4

V = I x R

Voltage (V) = Current (amps) x Resistance/Impedance (ohms)

For this formula, need to pay attention to whether the question has provided amps, mA, or uA (or ohms, kOhms, or MOhms) to give answer in the appropriate units

-Ohms = Amps (A)
-kOhms = Milliamps (mA)
-MOhms = Microamps (uA)

Question 5

Battery capacity formula

Answer 5

Capacity = I (current measured in amps) x T (time measured in hours)

This means battery capacity is measured in Amp-hours (Ah)

Question 6

Charge time formula

Answer 6

Charge time = E/P

E = programmed shock energy (J)
P = charging power from the battery (watts)

Question 7

Battery longevity formula

Answer 7

Longevity (years) = 114 x (battery capacity (A h) / current drain (uA))

Question 8

Current drain formula

Answer 8

Current drain (uA) = battery capacity (A h) / time (years)

Measured in microampere (microamps)